Biological materials (leather, fur, scales, grasses and other plants, etc) use for projects/crafts/clothings/etc can be bent to his will and shaped as needed with minimal need for cutting and patching. It does not work with anything synthetic or inert like plastic, metal, or stones, and does not work with living creatures (but CAN work with their fur/feathers/hair to an extent). It's like the material "wants" to be shaped rather than him forcing it one way or another.