Place your leather strap where you want it to be on your bag, then sandwich the strap between the two leather washers, lining up the holes. Thread the cord through one hole, and then through the second, going through all the layers of leather and fabric, and tie a double knot to keep everything in place. You can choose to have the knot on the outside or the inside of your bag. When you need to wash your bag, simply remove the leather straps.