I had been looking for hooks for threading finer reeds and heddles. I was not happy with the tools in the shops, and did not seen anything that seemed suitable. But, I am an old one, and thus I have old files, with old hanging file folders that are falling apart. It turns out the steel hangers in the file folders are thinner than the brass sleying hooks, soft enough to work easily with a bench grinder and file, but hard enough to make good tools. And they are cheap; and well it is a virtue to reuse and recycle.
Yes, I have a sleyer, but it does not work for finer reeds.
I also find the hooks make tieing weaver's knots on fine threads easier. Make a loop around the tool, use the hook to pull a bight of the standing end through the loop. Now you have a loose slipknot around the tool. Use the hook of the tool to pull the other thread into the loop of the slipknot, and sliding your fingers over the loose slipknot, tighten it. The loose knot will easily convert from a loose slipknot around a thread into a weaver's knot. It is good for lace weight and finer, and I can easily tie a sheet bend on anything thicker without a tool.