When it comes down to it there is nothing better than manual tools for your Lock pick Set, whether they be retail, homebrew, macgyver style. DIY'ers look here.
I seems obvious, but if you have a "checkering file", these make the perfect small serrations on the end of your tension tool. I purchased an old #1 checkering file at a garage sale. It cuts 40 Lines Per Inch which seems fine. While these teeth can be carefully cut in other ways, if you get yoyr hands on a checkering file, snap it up. Pete Sioux Falls
Some of us have used an old trick - use wire cutters to pinch notches on both sides at the same time. You are accomplishing the same idea, but there is less risk of damage to the keyway from sharp edges left by files.
Gordon
Just when you finally think you have learned it all, that is when you learn that you don't know anything yet.
The cutout were to fit into a tiny Master No.7, and then notched again to fit the very bottom of a paracentric Corbin-Russwin. I just filed some parts away so my pick could get some maneuvering room. I thought it was only for one lock.. but I now keep it in case it becomes useful again on something similar.
I'll knock down the "sharpness" of those teeth, or make them a bit less shallow. Mainly I like the appearance of how small evenly spaced the teeth are.
So the shape of the tension wrench is a combination of two different situations. I was trying to figure out which lock would have required such an unusual shape... Now it makes sense, thank you for the explanation.