US Patent 7850390 Frame with self-locking joint

A frame is comprised of plural frame members, each of which has plural projections and plural recesses in opposed relationship to the respective projections of the corresponding frame member. The frame is assembled by snapping selected ones of the frame members together so that the projections of a selected one or more of the frame members are urged into nesting engagement with the recesses of a selected other one or more of the frame members. Selected ones of the frame members are equipped with locking tabs to maintain the frame members in their assembled configuration and to counteract a force tending to disengage the projections from the respective recesses.