[Semper Paratus]

The hole is for a roll pin. Essentially you have two choices....Go buy a 1/16" diameter(you can use a 1/16" drill bit to verify the hole size) roll pin a roll pin punch and something to trim the roll pin off with. Install the pin scribe the length, remove the pin trim and reinstall, perhaps with a drop of blue loc tite. The other option is degease the sight and dove tail, raise a burr or two on the bottom of the sight to snug the fit up and reinstall with blue or red loctite. Be advised the use of red will take a source of heat to soften the loctite to be able to remove the sight. I've done both, both work well. I'm sure the experts will be along to provide other options that I'm not bright enough to comprehend.