[murmur]

It means you need to have leathercrafting SKILL also (not just materials). For example, Scorpion Harness, the crafter has to have around lv69 bonecrafting and lv44 leathercrafting. If the crafter has too low a leathercrafting skill, they will fail, even if their bonecrafting is 100. Let's say you make that with 42 leathercrafting (your bonecrafting can be a little lower or anywhere higher)... you have a good chance of gaining skillup for leathercrafting from making scorpion harness up to a cap of lv44.