Glossary of Terms
Related to Child Restraint Systems*

3-point harness – A harness found on infant-only restraints consisting of shoulder straps coming together at a buckle in the shell or on a crotch strap; not to be confused with 3-point (lap-shoulder) vehicle belts.

5-point harness – A CR harness that has a webbing strap over each shoulder, one on each side of the pelvis, and one between the legs, with all five coming together at a common buckle.

Acceleration – A measure of how fast a body (mass) gains or loses velocity as the result of a force being applied to that body.

Adjustable upper anchorage (AUA) – A system built into the vehicle that raises or lowers the shoulder beltanchorage to help place and keep the belt crossing the shoulder between the neck and arm; not to be confused with Upper anchorage; also called “adjustable upper guide.” See also Shoulder belt positioner.

Adjuster – See Pushbutton adjuster, Slide adjuster, Tilt-lock adjuster.

Anchor – A common short alternative for anchorage; often used to refer specifically to the hardware installed at the anchorage, either factory-installed or in a retrofit shoulder-belt or tether kit.

Anchor bar – A common alternative for lower anchorage.

Anchor point – A location identified in a vehicle where anchorage hardware, usually for a retrofitted top tether anchorage, may be installed.

Anchorage – A strong point and associated hardware in a vehicle to which a vehicle belt or LATCH attachment is secured. See Adjustable upper anchorage, Child restraint anchorage system, LATCH anchorage, Lower anchorage, Top tether anchorage, Upper anchorage.

Automatic locking retractor (ALR) – A vehicle belt retractor that allows the belt to be pulled out initially but locks when the pull-out action stops and tension is again applied. See also Emergency locking retractor,Switchable retractor.

Backless booster – See Belt-positioning booster.

Backless child restraint – A type of booster, as defined by FMVSS 213, that has a seating platform and a structure in front of the child for restraint, but which is subject to crash testing using only a lap belt and to the head excursion limit of only 813 mm.

Belt – See Vehicle belt.

Belt-positioning booster (BPB) – A firm platform, used with a lap-shoulder belt, that raises the child so that the height of his thighs and shoulders are closer to those of an adult and helps route both portions of the lap-shoulder belt to fit the smaller body; can be backless or have a high back, usually with a shoulder belt guide. See also Combination seats.

Belt-sensitive retractor – See Webbing-sensitive retractor.

Belt-shortening clip – Metal hardware used to fix the length of a lap belt with emergency-locking retractor, by securing a loop of belt from slipping through the clip; formerly called a "heavy-duty" locking clip. See also Locking clip.

Belt tightener – An aftermarket device, not regulated by FMVSS 213, designed to wind up excess webbing and hold a fixed length in place.

Bight – See Seat bight.

Booster – See Backless child restraint, Belt-positioning booster, Combination seat, Shield booster.

Built-in child restraint system – A CR designed to be an integral part of and permanently installed in a vehicle.

Car bed – An infant restraint that allows the baby to lie flat, with the long axis of the child’s body perpendicular to the direction of travel and head away from the door, the primary restraint surface being the side of the bed; primarily used with low birth weight infants and those with special medical needs.

Car seat – A common alternative term for child restraint system, especially when speaking with general audiences; easily confused in written material with “vehicle seat,” unless spelled as one word: "carseat."

Chest clip – See Harness retainer clip.

Child restraint anchorage system – A standardized system of user-ready hardware in vehicles, consisting of two lower anchorages and one upper anchorage specified in FMVSS 225, for installing child restraint systems independent of the vehicle seat belt; referred to as LATCH in the U.S. and similar to the Canadian Lower Universal Anchorage System.

Child restraint fixture (CRF) – A physical model representing the outside dimensions of a combined rear-facing and forward-facing child restraint (see FMVSS 225, Figs 1 and 2) that is used by a vehicle manufacturer to determine the space required by child restraint systems in a given seating position and the location and accessibility of the lower anchorages in that position.

Child restraint system (CRS or CR) – A general term in FMVSS 213 for a device designed "to restrain, seat, or position children who weigh 50 pounds of less" used primarily with professional and technical audiences.

Child safety seat (CSS) – A common alternative term for child restraint system used primarily with general audiences.

Child seat – A common term for a CR that only faces forward and has an internal harness. See also Combination seat.

Cinching latchplate – A latchplate on a lap-shoulder belt that will meet the “lockability” requirements of FMVSS 208 but will allow the belt to slip during a crash, making it necessary to remove all slack from the shoulder portion of the belt when used to secure a CR. See also Locking latchplate.

Clip – See Belt-shortening clip, Harness retainer clip, Lap belt clip, Locking clip, Shoulder belt guide.

Combination seat – A forward-facing CR or child seat that has a removable harness and can also be used as a belt-positioning booster.

Comfort guide – See Shoulder belt positioner.

Connector – Hardware at the end of a LATCH attachment, such as a top tether hook specified in FMVSS 213 or other latching device compatible with lower anchorages specified in FMVSS 225, that enables the CR to be securely fastened to a LATCH anchorage; can be either a hook-on connector or a push-on connector (lower attachments only).

Convertible child restraint – A CR that can be used rear-facing for infants up to at least one year and 22 lb or as much as 35 lb, and then turned to face forward until the child reaches the product's upper weight limit, at least 40 lb.

Emergency-locking retractor (ELR) – A vehicle belt retractor that locks only when the vehicle stops suddenly, often including sudden braking. See also Switchable retractor.

Flexible attachment – A lower attachment that includes webbing and usually a manual length adjuster.

Free-sliding latchplate – A latchplate on a lap-shoulder belt that allows the belt to slip easily between the lap and shoulder portions and therefore does not meet the “lockability” requirements of FMVSS 208. See also Locking latchplate.

Funnel guide – A device incorporated with some LATCH system lower anchorages to help the user position and guide the lower attachment connectorduring CR installation; also called a “guidance fixture.”

Harness – The webbing assembly attached to a CR shell or frame that restrains the child in a crash; also an independent restraint system made entirely of webbing (with fasteners and length adjusters), often referred to as a "child harness," and subject only to the head excursion limit of 813 mm.

Harness retainer clip – A plastic or fabric device that holds the shoulder straps of a harness in place on the child's chest for pre-crash positioning; not required, defined, or regulated by FMVSS 213; also called a “chest clip.”

Head excursion – The distance that the head of a child or crash dummy moves in the direction of impact or on rebound from a crash; regulated forward limit for most forward-facing CRs, measured from the test bench pivot point, of 813 mm (no top tether allowed) and 720 (top tether allowed).

Head Injury Criterion (HIC) – A calculated value, using a complex formula related to the magnitude and duration of dummy head acceleration, with or without direct head impact, that indicates the likelihood of serious head injury.

Heavy-duty locking clip – See Belt-shortening clip.

Hook – See Hook-on connector, Top tether hook.

Hook retainer spring – The leaf spring that closes the opening in a hook-on connector or top tether hook.

Hook-on connector – A top tether hook, or hardware at the end of a lower attachment that resembles such a hook.

Infant-only restraint – A restraint system that only faces the rear of the vehicle, traditionally has a back height (rump to top of shell) of 18" or 20", and is generally limited to children weighing up to 20 or 22 lb.

Integrated CR – See Built-in child restraint system.

ISOFIX – A system for the connection of a CR to a vehicle that has two lower anchorages in a vehicle seating position located near the seat bight, corresponding rigid attachments on the CR, and a means to limit the pitch rotation of the CR; defined by ISO 13216-1 and adopted by European countries; differs from LATCH and LUAS in that only rigid attachments are allowed and top tethers are not required.

Lap belt – A vehicle belt that restrains the lower torso (pelvis); may be a lap-only belt or a portion of a lap-shoulder belt; referred to as a Type I belt system in FMVSS; can be used to secure a CR.

Lap belt clip – A piece of plastic to fasten the loose end of a manual lap-only belt to the main part of the belt.

Lap-shoulder belt - A vehicle belt that restrains both the lower and upper torso, usually with a continuous loop of webbing connected to a buckle with a latchplate; referred to as a Type II belt system in FMVSS; can be used to secure a CR; term may be substituted by the phrase “lap and shoulder belt” in instructions and other communications on routing and use to emphasize both segments of the belt.

LATCH – An acronym that stands for "Lower Anchors and Tethers for CHildren" and refers to the child restraint anchorage system specified in FMVSS 225 and the corresponding top tethers and lower attachments identified in FMVSS 213. See also ISOFIX, Lower Universal Anchorage System.

LATCH anchorage – Hardware in the vehicle to which a top tether or a lower attachment is connected as part of a complete CR installation.

LATCH attachment – A hardware assembly on a CR, possibly including webbing, that connects to a top tether anchorage or a lower anchorage as part of a complete CR installation. See also Connector.

Latchplate – The metal portion of the vehicle belt assembly that connects to the buckle and through which the webbing is threaded; the insertion tip is also called the "tongue." See Free-sliding latchplate, Cinching latchplate, Lockability, Locking latchplate, Switchable latchplate.

Lock-off device – A clamp attached to the CR that is affixed to the vehicle belt to maintain tension on the belt, to prevent movement of the webbing relative to the latchplate and/or to prevent movement of the CR relative to the webbing; may be used in place of a locking clip with a lap-shoulder belt or, in a few U.S. rear-facing models, with a lap-only belt to improve lateral stability and coupling to the vehicle; defined in ECE R44.03 as "a device which locks and prevents movement of one section of the webbing of an adult safety-belt relative to another section of the webbing of the same belt” and is applicable both to CR installation and to belt-positioning booster use.

Lockability – Beginning with the 1996 model year, a regulated feature requiring that the lap portion of a vehicle belt "can be used to tightly secure a child restraint system" without "any device that must be attached by the vehicle user to the seat belt webbing, retractor, or any other part of the vehicle," and "shall not require any inverting, twisting or otherwise deforming of the belt webbing" (FMVSS 208, S7.1.1.5).

Locking clip – Metal hardware used to hold the lap portion of a lap-shoulder belt from lengthening during normal driving by clamping the webbing together next to the latchplate; also called a "regular" locking clip. See also Belt-shortening clip.

Locking latchplate – A latchplate on a lap-shoulder belt that, when buckled, will allow the lap portion to be pulled into the shoulder portion but will restrict its slippage back to the lap belt; a latchplate on a lap-only belt that restricts slippage once the belt is buckled and pulled tight; meets the “lockability” requirements of FMVSS 208.

Lower anchorage – One of two horizontal rigid bars 6 mm in diameter and 25-40 mm long specified in FMVSS 225, installed in vehicles in or near the seat bight, and to which one of two lower attachments is connected to secure the lower part of the CR. See also Child restraint fixture (CRF), Funnel guide, LATCH anchorage.

Lower attachment – One of two hardware assemblies on the CR, possibly including webbing (or a single assembly with a connector at each end) that enables the CR to be securely fastened to one of two (or both) lower anchorages. See also LATCH attachments.

Lower connector system – Term used in Transport Canada regulations for lower attachment.

Lower tether – A strap and hardware assembly attached near the back and base of a large rear-facing CR and attached to the vehicle seat track or other low anchorage to restrict rotation of the CR toward the rear of the vehicle; used primarily in Scandinavian markets.

Lower Universal Anchorage System (LUAS) – Term used in Transport Canada regulations for a system similar to LATCH.

Misuse – Any deviation from the intended application and use of a CR that might reduce its protective performance.

Overhead shield – A curved plastic bolster attached with pivot arms to the sides of a CR shell and which is in turn attached to shoulder straps and held down by a crotch strap and buckle, forming a complete CR harness system; also called a “tray shield.”

Push-on connector – Hardware at the end of a lower attachment, usually with a spring-loaded latch, that automatically locks around the rigid bar when pushed onto a lower anchorage.

Pushbutton adjuster – A strap adjustment mechanism that releases its hold on the webbing for the purpose of lengthening the strap when a button is depressed; does not inhibit the strap from being shortened when the free end of the webbing is pulled.

Retractor – See Automatic locking retractor, Emergency locking retractor, Switchable retractor, Webbing-sensitive retractor.

Rigid attachment – One of two hardware assemblies, built into the CR base at 280mm apart, that meet the requirements of ISO 13216-1 and are used to connect a CR to a lower anchorage; a lower attachment also allowed in LATCH and LUAS.

Safety belt – See Vehicle belt.

Seat belt – See Vehicle belt.

Seat bight – The intersection of the vehicle seat back and bottom cushions, where vehicle belts frequently emerge and where or near where lower anchorages are placed.

Shell – The molded plastic structure of a CR that positions the child in the harness and is either strong enough by itself to provide impact protection or, in some models, is reinforced with a metal frame.

Shield booster – A type of backless child restraint, which is subject to testing using only a lap belt and to the head excursion limit of only 813 mm.

Shoulder belt - A vehicle belt that restrains the upper torso; is most commonly a portion of a lap-shoulder belt, but may be a shoulder belt alone in some older vehicles; the latter cannot be used to secure a CR.

Shoulder belt guide – A slot, hook, loop, or clip attached to the side of a highback belt-positioning booster, or a clip on an adjustable strap attached to a backless BPB, through which the vehicle shoulder belt is routed to help place and keep it crossing the shoulder between the child's neck and arm.

Shoulder belt positioner – Built-in or aftermarket device that helps place and keep the vehicle belt crossing the shoulder between the neck and arm. See also Adjustable upper anchorage; also called a “comfort guide.”

Slide adjuster – Hardware to lock a strap at a fixed length using a metal plate or pair of plates with slots through which the strap is threaded in a prescribed manner; may use one slide with three slots or two slides with two slots each; strap must be detached and webbing loops manually loosened to either shorten or lengthen the strap.

Submarining – The motion of an occupant when one or both hips slide under the lap belt, so that the belt applies crash forces to the soft abdominal area between the pelvis and ribs.

Switchable latchplate – A latchplate on a lap-shoulder belt that can be converted from a free-sliding to a locking latchplate for CR installation.

Switchable retractor – A vehicle belt retractor that can be changed from an emergency-locking retractor to an automatic-locking retractorfor tight installation of a CR. See also Lockability.

T-shield – A flat, plastic pad on a fairly rigid stalk or webbing strap that buckles into the shell between the child's legs and is attached to shoulder straps, forming a complete CR harness system.

Tether – A common short alternative for top tether, in markets where lower tethers on large rear-facing CRs are not used.

Tilt-lock adjuster – A strap adjustment mechanism that releases its hold on the webbing for the purpose of lengthening the strap when the hardware is held at an angle relative to the webbing; does not inhibit the strap from being shortened when the free end of the webbing is pulled.

Top tether – An assembly consisting of a top tether strap, attached at or near the top of a CR, together with a length adjuster and a top tether hook, that is used along with either a vehicle belt or lower attachments for complete installation of a CR in a vehicle.

Top tether anchorage – Hardware component, such as a ring, bar, bracket, or webbing loop, and its underlying structure in the vehicle, either user-ready or aftermarket-installed, to which a top tether is attached.

Top tether hook – A metal connector specified by FMVSS 213 to attach a top tether strap to a top tether anchorage.

Top tether strap – A straight or V-shaped length of webbing attached at or near the top of a CR as part of a top tether assembly.

Tray shield – See Overhead shield.

Type I belt – See Lap belt.

Type II belt – See Lap-shoulder belt.

Upper anchorage – Term used in FMVSS 225 for top tether anchorage.

Vehicle belt – A webbing, buckle, latchplate, and length-adjustment (usually a retractor) assembly installed in the vehicle that is used to restrain an occupant or a CR; also called a “safety belt” or “seat belt”; may consist of a lap belt only, a combination lap-shoulder belt, separate lap and shoulder belts, or less commonly a shoulder belt alone with a knee bolster.

Vest – See Harness.

Webbing-sensitive retractor – A type of emergency-locking retractor that is activated by a sudden pull on the belt.


ECE R44-03, Uniform Provisions Concerning the Approval of Restraining Devices for Child Occupants of Power-Driven Vehicles ("Child Restraint System"), June 1998.

Federal Motor Vehicle Safety Standards

   FMVSS 208, Occupant Crash Protection. 49 CFR 571.208. October 2003.

   FMVSS 213, Child Restraint Systems. 49 CFR 571.213. October 2003.

   FMVSS 225, Child Restraint Anchorage Systems. 49 CFR 571.225. October 2003.

ISO 13216-1. Anchorages in Vehicles and Attachments to Anchorages for Child Restraint Systems – Part 1: Seat Bight Anchorages and Attachments. March 2000. 

ISO 13216-2. Anchorages in Vehicles and Attachments to Anchorages for Child Restraint Systems – Part 2: Top Tether Anchorages and Attachments. Draft May 2003.

National Highway Traffic Safety Administration. Child Occupant Protection Glossary. In National Standardized Child Passenger Safety Training Program - Instructor Guide, p. A-8 - A-14. 2004 (in press).

Stewart DD, Kern KC. LATCH...The Essential Guide. 3d ed. Safe Ride News Publications, Seattle, 2003.

SafetyBeltSafe U.S.A. Child Passenger Safety Technical Encyclopedia. 2004.

Transport Canada, Motor Vehicle Restraint Systems and Booster Cushions Safety Regulations (RSSR).

Transport Canada, Motor Vehicle Safety Regulations

   Standard 210.1, User-Ready Tether Anchorages for Restraint Systems.

   Standard 210.2, Lower Universal Anchorage Systems for Restraint Systems and Booster Cushions.

*This glossary was developed and is under continuous revision in consultation with members of the
Society of Automotive Engineers, Children's Restraint Systems Standards Committee

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