A low elevational profile of each of a pair of first and second wheel chocks for restraining a current “low-drag” motor vehicle in a carrier, such as a railway car, is derived from each wheel chock having an internally webbed, elongated stepped-box body terminated with a relatively short rectangular box having its inner wall integrally formed with the stepped-box body. The body of the first chock is essentially a mirror-image of the second chock body. The low profile of a wheel chock allows each to be positioned under a vehicle the rocker panel of which has its lower edge only 148 mm (5.82 inches) above the surface upon which the vehicle's tire rests, so that the installed chock height is reduced to 47.6 mm (1.87″) under the components of the vehicle's body. The assembly may include a pair of “active” chocks; or, one active chock and one anchor chock. A single window in the upper portion of the stepped-box provides access for a strap of a wheel harness, which strap is wrapped around a torque tube in an active chock. The torque tube in one chock is rotatable in a direction opposite to that of the torque tube of the other chock. With a pair of active chocks, hooks on straps of a prior art harness are eliminated because it is difficult and time-consuming to manipulate a tire harness with its straps and hooks to secure the tire between the wheel chocks. When one chock is an anchor chock, one end of the strap is provided with a hook which is anchored to a rod or tube which is substituted for the rotatable torque tube.