An assembly for a truck at a loading bay includes a guide track and a chock member for the truck which is reciprocated along the guide track to engage the rear wheels of the truck and lock it securely in position; the guide track may be formed in a platform forming part of the assembly and on which the truck is supported; suitably the platform is hinged at its outer end whereby the platform is pivotable about the outer end such that the rear of the truck may be elevated or lowered for alignment with the loading bay.