I use Stabilo Aquarable for Kydex prototype layouts on most knives or holster I make. Works great to make detailed markings for layout but can easily be washed with water and a little soap on most hard materials. I keep a few dozen of these in my supplies. Only issue you can run into is when they're dropped or banged up during shipping in inside marking materials cracking causing sharpening to be more difficult. These pencils need regular sharpening and wear quickly but that's to be expected for the use of these. If you're using on a warmer surface they are going to wear down even more quickly. One r Or 2 small lines on a material at around 100 will melt these to the wood. Cooler the material the better off you are for breaking down of the pencil