Blue jeans pant leg, well used. The jig is a milled fixture that fits a few iPhone models, you can see the hold down areas for 4, 4s in the unused half. The jeans material is actually a good thing to use for soldering, as you clean the irin tip quite well just by wiping against the material. Even works while wearing them for a quick wipe, though you really should not do it if you are wearing shorts instead of jeans. I have often done soldering with a board balanced on my knee and being held by the other leg. Wipe iron on pant leg, tin and solder fast before flux is cooked off.