A truck must not leave the loading dock before loading is complete. Doing so can cause serious injuries to the workers and damage to the forklifts and cargo. A trailer restraint assures that the truck will remain at the loading dock.

Trailer restraints come in two designs: Autochock (Fig. 51) blocks the trailer's wheel and the STAR Restraint (Fig. 52) engages the rear under ride protection bar (ICC Bar) of the trailer. Since the Autochock does not rely on an under-ride protection bar at the rear of the trailer, its application is more universal.

Trailer restraints can also include a light system that informs the dock worker when the restraint is engaged and tells the truck driver when it is safe to dock or leave.