A pipe cap is a fitting with a female (inside) thread. It is used like a plug, except that the pipe cap screws on the male thread of a pipe or nipple. A cap may have a solvent weld socket end or a female threaded end and the other end is closed off. If a solvent weld cap is used to provide for a future connection point, it must be left several inches of pipe before the cap (as when the cap is cut off for the future connection, there will need to be enough pipe present to glue a new fitting onto).

Available in a wide range of sizes, caps can be made from Aluminum, Delrin, Ethyl Vinyl Acetate Monel, Nylon, Polyetheretherketon (PEEK), Polyethylene (PE), Polypropylene (PP), Silicrub Styrene Butadiene, Steel Stainless steel etc.

The industrial caps can be round; square; rectangular; "U" shaped; "I" shaped and have Round Hand Grip or Flat Hand Grip.

Features of these caps are that they can be: