The invention relates to a mast assembly for a construction machine with a mast (12), which has a mast guide (14), along which a mast carriage (20) is movably mounted, which is connected to a hydraulic source and has a first hydraulic coupling part (24) for hydraulically connecting a tool unit (40) with a hydraulic source on the mast carriage (20). According to the invention, it is provided that the tool unit (40) has a tool guide device (46), with which the tool unit (40) can be attached and positioned on the mast guide (14). On a frame (42) of the tool unit (40), a second hydraulic coupling part (44) is arranged, which corresponds to the first hydraulic coupling part (24) of the mast carriage (20). When the mast carriage (20) and tool unit (40) are moved together along the mast guide (14), the first hydraulic coupling part (24) of the mast carriage (20) can be hydraulically connected to the second hydraulic coupling part (44) on the tool unit (40). A locking device (60) is provided, which is spaced apart from the hydraulic coupling parts (24, 44) and has at least one hydraulically actuated locking bolt (62), with which the frame (42) of the tool unit (40) can be mechanically connected to the mast carriage (20). The invention further relates to a corresponding method for connecting the tool unit to the mast carriage.
