what is a "pair"

I started a new photo project this weekend involving the idea of pairs of things when I walked by the example above of two crossed pieces of tape. I immediately dismissed it as not an example of a pair of things and walked on, then stopped and thought, wait a second, why isn't that a pair?

To me, there's something about the fact of crossing that blocks this as being a pair of tapes. However, the phrase a pair of scissors is just fine and that involves two crossed things and a pair of pants is fine and that involves two things sewn together. However, in those two cases, I don't really decompose the constituent semantically. I treat it as a whole. It's simply a historical coincidence to me that we use the word pair. I don't really think of scissors and pants as a true pair of things.

Now, the nuts and bolts below, those are clearly pairs to me.