I think this is self-explanatory but some readers have asked for a picture, so here it is. I used a 10-32 hex bolt cut off so it's flush on the inside of the receiver. You don't want the rear of the bolt to strike it. To make it more pleasing to the eye I have used smooth sided hex bolts on some of my Marlin model 60 rifles. You could also counter drill the hole so the head sits a little lower. The scope will NOT slip to the rear with this stop bolt installed.