J-Hooks allow for secure contraction and expansion of piping system. The two ring-shank nails are provided for secure installation. They are made of high impact corrosion-proof ABS resin. They can be used on all Schedule 30 and 40 piping to support drain, waste and vent piping from rafters and joints. J-Hooks can be used on all copper, PEX, CPVC and other CTS/DWV sized piping.