The wooden pieces from the pedals to the axle are called the 'chain stays'. I made them out of hard maple, sandwiched between 1/4" African leopardwood planks for an interesting accent. The wooden pieces from the seat tube to the axle are called 'seat stays'. They are made from curly maple and black walnut, same as the front triangle. The aluminum pieces holding the tire axle are called 'dropouts'. I made them from 1/4" plate aluminum, polished to a satin sheen.