[Lawrence Coppari]

Think of a small banjo with a hollow bolt through the part where you pick it. The head of the bolt has a crush washer between it and the banjo part. There is another crush washer on the other side of the banjo. The remainder of the hollow bolt is threaded into a pipe or something where there is a fluid of some sort. The portion of the hollow bolt inside the banjo has radial holes that permit the fluid to flow into the banjo part. The banjo is connected to another tube, usually flexible, by a nipple. This is the part of the banjo where you change the notes by holding the strings to the instrument to shorten their length. The fluid goes up the handle or whatever you call it on a banjo. It is a way to tap into a fluid in a pipe or add another fluid to a pipe. The crush washers make the seal.