As long as your flint hits the frizzen at about 1/3 (+ or -) down from the top at more or less a 60 degree angle it's installed about right. Some locks like the flint bevel down to get this geometry correct. Flints can be reversed, flipped upside down and, of course, knapped. I've had a few flints that were DOA and worthless. I've had them give upwards of 100 shots with nothing done but moving it forward in the jaws as it got too short. Mostly I get up to double the number of shots from a flint by knapping. Every hunting season sees a fresh flint installed in the lock, but I keep all old ones for less serious use.