Abstract: A cam assembly for detachably locking a structural member includes a pivot axle, a cam body having a locking cam surface adapted to make locking contact with the structural member and a curved surface comprising a circular arc segment and another segment offset from the arc segment, a locking latch pivotably movable relative to the pivot axle and cam body between locked and unlocked positions and having a contact surface facing the curved surface of the cam body, and a roller disposed between the contact surface of the locking latch and curved surface of the cam body. The roller is supported on the circular arc segment of the curved surface when the locking latch is held in the locked position such that the distance between the pivot axle and curved surface is filled by the locking latch and roller and play is eliminated between the cam body and pivot axle causing the locking surface of the cam body to make locking contact with the structural member and hold the cam assembly in a self-locking state.