During a tong jaw change-out operation on a rig floor, a crew member tapped the tong jaw into position using a rubber mallet to insert the pin while two other crew members held the tong to stabilise it. He started with series of taps then swung with more force as one of the assisting workers adjusted the jaw but with his hand in the path of the mallet. The mallet struck the worker’s right hand, fracturing his middle finger.