Hinge shims are used to re-align your doors. Doors that are mis-aligned bind on the door frame which causes difficulty in opening and closing. Hinge shims are made of high impact plastic, far superior to cardboard shims which compress over time. Installation: They are installed under the hinge leaf Each shim allows for 1/16" of adjustment. To achieve more adjustment, simply increase the number of shims. The door and hinge do not need to be removed to install the shims. Shims are installed by removing two screws and loosening the others. Shim is slipped inbetween the hinge and door or frame. Hinge screws are replaced and tightened. Available in 3 sizes and sold by the pack. Shims are color coded for easy size recognition: For 3.5" hinges, shims are white (18 shims per pack) For 4" hinges, shims are gray (15 shims per pack) For 4.5" hinges, shims are black (15 shims per pack)