I find that the best tool for adjusting the bit height on a table router is a 6" steel rule with fractional increments on its end. The only problem is holding the rule on edge, since my hands are both occupied adjusting the router. To create a “third hand,” I kerfed a block of wood to squeeze the blade and hold it on edge while I adjust the bit height to the end increments. (I made the cut with a hacksaw, but any saw whose kerf equals the rule’s thickness will do.) Use the same trick to stand straightedges for adjusting jointer knives and aligning surfaces.
