In engineering, a shim is a thin an often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear. The term comes from a Kentish word of unknown origin, dating to at least as early as 1723, meaning "a slip of wood." Originally a piece of iron fitted to a plow for scraping soil; meaning "thin slip to fill up a space or raise a level" is from 1860. The verb meaning "to wedge up a surface by means of a shim" is attested from 1937.