I put some clear plastic bench dogs in the large & small CNC tool boxes. They are made on a 3D printer using PETG plastic (that is soda bottle plastic) with 50% infill. They should be less destructive to your end mill if it was to run into one. Use them, don’t use them, the choice is yours. If you do use them then any comments or suggestions are appreciated. If you chew one up please send me a direct-message (@bwatt) so I can make another to replace it.
Sample of some black ones, similar to the clear ones:
