I was thinking of using square nut and cartridge-bolt. I change my
mind:

- I think a T-nut is better than using a square nut. Then I don't
need to chisel a square for the square-nut, and I don't need to epoxy
it in place.

- I think a cartridge bolt will lose its bite on the wood sooner or
later if I turn it often. I think I will use a threaded rod and bend
it onto the wood to secure it.

Great! Seem like I get the idea.

Jay Chan