An employee was helping the knuckle boom operator to unjam a log on the conveyor. The employee attempted to rig a chain around to the log and back to the knuckle boom, but the chain did not reach the knuckle boom. When the knuckle boom operator made a minor adjustment to the boom, the grappler attachment swayed on its swivel joint and pinned the employee's right ring finger against the conveyor's side wall. The fingertip was crushed and surgically amputated to the second knuckle.