Found this very detailed video on how to measure a handgun to accurately design a friction hold pancake holster. Useful stuff and hard to find online. Discusses clearances, adjustments for leather weight, protrusions like co-witness sights, et al.
These same techniques could be adapted for making a belt holster for an oddly-shaped tool like channel locks or a drill.
Note that this style of holster would be cut and stitched, and then wet-molded to the handgun for a precise friction hold.
