a piece added at the end; an appendage

a triangular piece from which the strings of a stringed instrument are stretched to the pegs

an ornament placed below the text on a page, e.g. at the end of a chapter

Well … if I am to turn over a new page, this may figure as a tail-piece to the old — Henry James

a short beam or rafter with one end fastened in a wall and the other end supported by a beam across an opening