Volumes: Sometimes called piggy back holds, they are an extremely large type of hold that any variety of holds can be attached to. The volume is attached to the wall, and it has pre-placed t-nuts in it to which other holds can be attached. Volumes were at one time made from wood, but now they are also made in a variety of materials (including fiberglass, coated wood, resin, urethane, and molded plastic) by several climbing companies. Volumes are especially prevalent in Europe and on the World Cup circuit, where sometimes entire routes will be constructed from them. To imitate these textured World Cup volumes, sandpaper can be placed on homemade wooden volumes to create texture and allow climbers to make use of the volume’s features.