Recently pick up at TC #7190 tang mounted sight i intend to put on my Hawken. The instructions say to use the rear mounting hole in the tang for one screw ( the wood screw into the stock) and then drill and tap the tang for the front screw. After taking a look at mine, it already has a hole drilled and tapped there with a plug in it. Anybody know if this is what the hole is for, and if so, what screw is necessary to mount the sight to it.