a cart includes a frame , a leg attached to the frame , and a wheel movable relative to the frame . a handle is operatively associated with the wheel and with the frame , whereby the work surface is in a normally stationary , inoperative position , and positive movement of the handle causes the wheels to engage the floor and place the work surface in an operative , movable mode . the work surface is engineered so that it is automatically returned to its stationary mode when no user is actively placing the work surface in its movable mode .