Abstract: A locking system for mechanically locking a backhoe boom in a transport position on an earth moving machine. The boom is supported for swinging movement about a horizontal pivot carried on a swing post coupled by a vertical pivot to a frame structure of the earth moving machine. The locking system comprises a lever fulcrummed intermediate its ends on the swing post. The lever has at one of its ends a latching element engageable with the boom in a raised position of the latter to prevent downward swinging movement, and at the other of its ends a latching element simultaneously engageable with the frame structure to hold the swing post and thereby the boom in a centered position. A manipulable actuator accessible at the operator's station is provided for actuating or releasing the boom locking actuator.