What is a Shim

A shim is a thin or wedged piece of wood or material that is used to fill small gaps between objects to provide a level surface, add support, or create a better fit. Shims are used when installing cabinets to help level base cabinets or keep wall cabinets flush. In cases of an uneven floor, for example, shims are used at the bottom of a base cabinet to keep the cabinet height or countertop level and consistent. Shims could also be used when installing a pre-hung door to make the door jambs level. Typically, shims are thin wood wedges about 1.5 inches wide and anywhere from eight to 16 inches long.