A trunnion is a part of the saw that connects the blade to the arbor. There are two types of trunnions used in the saw industry. One type is called a “trunnion pin” and the other is called a “pinless trunnion.” Both types of trunnions allow the blade to move up and down relative to the arbor. However, there are differences between the two types. Trunnion pins are usually made out of steel and are attached to the arbor using screws. Pinless trunnions are usually made out of aluminum and are attached to the saw arbor using bolts.