kentdvm recently posted an Instructable for a carpenter bee trap, http://www.instructables.com/id/Making-Carpenter-Bee-Traps/
which uses two bottle caps connected together as part of the assembly. He used tape to connect the bottle caps, and here I offer another method that uses 1/2-inch metal grommets from a tarp repair kit. Photo is of one of my own variations of the trap, designed to fit under a small roof overhang. A separate Instructable for this trap will be posted soon.
To see my related Instructables, click on my username wherever you see it on this page, or enter unclesam in the home page search box. On the new page, click "view all __ instructables." On the next new page, click "NEXT" repeatedly to page and scroll through them all.