In plumbing and pipefitting, "close" typically refers to a type of fitting, specifically a close nipple, that is very short and has virtually no unthreaded area.
When a close nipple is tightly screwed between two female fittings, the fittings come close to touching each other, and very little of the nipple remains visible. The threads extend almost the entire length of the nipple.
Essentially, a "close" fitting minimizes the distance between the two connected fittings.
Therefore, the key takeaway is that "close" describes a nipple's length and its resulting proximity between connected fittings.
