A rotating pin attached to a shoulder (friction stir tool) is used to stir a solid material during friction stir process. The pin is an extended tip of a solid cylinder (shoulder). The role of the shoulder is to prevent stirred materials from being extruded out of plane. In additive friction stir deposition, there is no pin while the shoulder has a thorough hole. The purpose of the hole is to pass the material onto a substrate from above. The material can be a rod, powder, or small blocks of any shape.