A shim is a thin, tapered or wedged piece of material used to fill small gaps or spaces within objects. They are commonly used to support, adjust for better fit, or provide a level fit. In many cases, shims are also used as spacers to fill gaps between parts subject to wear and tear. The material a shim is made from is known as shim stock. Common shim stock can be made from a variety of materials but is typically composed of wood, stone, plastic, metal, or even paper. Aerospace specific shims come from materials such as carbon steel, stainless steel, brass, copper, aluminum, titanium, and others.