While rigging up the V-door during a rig move, the driller was supervising two floormen who were assigned to install the V-door pins. The crane was holding the V-door in an inclined position and lowering it under the driller’s signals. The handrail attached to the V-door steps became stuck against the air hoist on the rig floor (driller did not notice it). The IP was installing the middle pin and another floorman was installing another pin beside him, the driller was helping them and giving signal to the crane operator at the same time to lower the V-door slightly to facilitate the installation of the pin. Suddenly the handrail got free from the air hoist and moved away fast and the V- door gate support hit the injured person’s (IP’s) left knee. The IP sustained a hematoma in his left knee and put his leg in cast for 2 weeks.