Commercial Driver's License Coupling Procedures

This set of vocabulary flashcards covers the step-by-step coupling procedures and terminology from Section 6 of the 2005 CDL Testing System manual.

Fifth wheel jaws

The locking components of the fifth wheel that must be in the open position before coupling.

Safety unlocking handle

A handle that should be in the automatic lock position during the initial inspection for coupling.

Sliding fifth wheel

A type of fifth wheel that must be locked in place before coupling a tractor to a trailer.

Trailer kingpin

The coupling pin on the trailer that must be checked to ensure it is not bent or broken.

Chock wheels

The action of placing blocks against trailer wheels to prevent movement, or ensuring spring brakes are on, before coupling.

Landing gear

The support legs of the trailer; backing at an angle can cause the tractor to push the trailer sideways and break this component.

Correct Trailer Height

A position low enough that the trailer is raised slightly by the tractor when the tractor is backed under it.

Glad hand seals

The rubber seals on air-line connectors that must be checked for damage before connecting tractor air-lines to the trailer.

Emergency air-line

The air-line from the tractor that connects to the trailer's emergency glad hand.

Service air-line

The air-line from the tractor that connects to the trailer's service glad hand.

Tractor protection valve control

A control in the cab moved from 'emergency' to 'normal' to supply air to the trailer brake system.

Crossed air-lines

A potential error in the brake system that must be checked after supplying air to the trailer.

Lowest reverse gear

The specific gear setting that should be used when backing the tractor slowly under the trailer.

Check Connection for Security

The process of raising the landing gear slightly and pulling the tractor gently forward while trailer brakes are locked.

Upper and lower fifth wheel space

An area that must have no space between the components during inspection; presence of space indicates the kingpin may be on top of the closed jaws.