I needed a rack to hold test tubes, but the one's I have seen don't hold as many as I'd like, and are rather expensive. I went to the local hardware store and found a wire shelf with holes that looked about the right size.
When I got it home and gave it a try, I found that it worked fairly well, but the tube bottoms were able to slide from side to side too much causing the tubes to end up crooked. I used some fine wire to make guides for the tube bottoms.
Much better. Works great, holds quite a few test tubes, and was inexpensive.