The nuts are fluted and a simple wrench can be made from two blocks of steel and a couple of bolts with nuts. To keep the nut fron turning in the round hole of thehomemade wrench a steel dowel is inserted in one of the flutes and a crresponding groove cut in the hole in the 2 blocks. The first time they are removed these nuts tend to be a bit stubborn. After that it gets a lot easier...