Train Forged Knuckle As one of the most important load-bearing parts, the train forged knuckle ;has a direct relationship with the safety in operation and reliability of the freight trains. Railway couplers are components designed for connecting rolling stocks on a train to transmit traction force and impact force, as well as to keep some distance between the rolling stocks. Knuckle throwers are a type of coupler. http://www.chunguangforge.com/train-forged-knuckle/