Ever since I started building double rifles, I've wanted a set-up that would give very precise adjustments and repeatability. I thought up this jig while hunting turkeys last week. I think that the photos will explain most of it. I started with a 1"x1"x6" piece of cold-rolled, milled a slot for the micrometers and gibs, and drilled holes for set screws. I went to the local cut-rate machine tool store and bought two 0-1" micrometers for $16.50 each. I hack-sawed off the anvil end of each and milled away some of the body in order to let them sit lower in the slot. This setup works even better than I had hoped for and allows adjustments of as little as .0005 if needed.