You could be correct about the humidity changing the diameter of the dowel. However, a well seasoned and well sealed ash dowel may well not have that problem. Time till tell.

Again, this is a poor man's version of this tool. Easily finding the correct diameter metal or plastic/nylon rod, without machining capability, may be rather difficult.

Maybe I should have called this the "poor CHEAP and EASY man's spar alignment tool"!

My $0.02 (or ZWD 10,000,000,000).

- John OHM Ω