A portable plural telescoping mast cable hoist mechanism is provided which incorporates a single cable for telescopically extending and retracting the mast sections and for controlling movement of a load handling carriage. A carriage lock mechanism is provided to prevent inadvertent movement of the carriage and movable mast sections while the cable hoist mechanism is being transported or otherwise moved about while positioned on its side. The carriage lock mechanism incorporates a freely pivotal carriage lock having a hook at its lower end which is normally positioned out of locking engagement with a locking pin and which is pivoted by gravity into locking engagement with the locking pin while the unit is lying on its side for transportation and handling, thereby securing the carriage and mast sections against inadvertent movement.