Fasteners join, or affix, two or more objects. Although they are usually used to attach pipe and fittings to mechanical supports in buildings, they do not connect the pipes. Fasteners commonly used with piping are a stud bolt  with nuts (usually fully threaded, with two heavy, hexagonal nuts); a machine bolt and nut; or a powder-actuated tool (PAT) fastener (usually a nail or threaded stud, driven into concrete or masonry).