Abstract: An anti-tip blocking device is disclosed for preventing the opening of more than one file drawer in a file cabinet at the same time. The device includes a plurality of locking bars and cam elements vertically stacked in a vertical channel one upon the other alternately to slide vertically therein. The cam elements are engaged by pins carried by the file drawers whereby opening of any file drawer requires additional vertical space in the channel to be occupied. With the free vertical space in the channel limited to the space required for the opening of one drawer, once any one drawer is opened, no other drawer may be opened. The improvement disclosed involves providing each cam element with a cylindrical bearing surface to contact the vertical channel so that the cam element is vertically slidably in the channel while being rotatable about the axis of the cylindrical bearing surface.