Add Glass Breaker/Point Contact to Glock 78-81 Knives Improvised Thread Mod in 10 Minutes! This is my MacGyver approach and improvised way to get you a bolt cap in a $30-$40 Glock knife. So I used a 1/2" circumference metal thread hex bolt, the tight thread for metal bolt, the chamber tube is made out of some form of hard aluminum it's not that hard, a tight thread hex bolt will bore the threads then get yourselves a new 1/2"X1/2" Hex bolt. Lockdown the bolt in your vise, then slowly groove in a little at a time and backing off maintaining your knife at straight angle and you'll need a pipe wrench. In my Glock knife here the chamber tube inside the handle is 1-1/2" deep and straight walled. When finished just fill the lanyard holes with silicone.