Abstract: A clamp assembly for releasably securing a cab or other truck toppers to a pick-up truck box includes master and slave assemblies mounted to a transverse section of the sidewall of the cab and spaced-apart from each other. Each assembly has an engagement member pivotable between an operative position in which the engagement member extends beneath an inwardly extending flange of the sidewall of the truck box and abuts the undersurface of the flange, and an inoperative position in which the engagement member clears the flange. A set of worm and worm gear is provided in the master assembly and a worm gear shaft extends through the master and slave assemblies to drive the engagement members in the pivotal movement. The clamp assembly is operated using a rotating tool from inside of the cab so that unauthorized removal of the cab from the truck is prevented.