Abstract: Two lifting units (1, 2) have lifting grabs (3) for lifting individual concrete slabs (29) off a prestressing bed on which they have been cast and then stacking them on a pair of support beams (6) to form a pile (28). Once the pile (28) has been formed, the lifting units (1, 2) use lifting hooks (16) contained within an upper frame (14, 15) to lock into the beams (6). A jacking mechanism (13) then raises the upper frames (14, 15) relative to lower frames (11, 12) to lift up the entire pile of slabs (28). The lifting units (1, 2) are mounted on rails (9) which run along the sides of the prestressing bed and lead off to a stockyard where the pile of slabs (28) is taken by the lifting units (1, 2) for storage. During transfer of the individual slabs (29) to the pile (28), drilling units (4) are swung under each slab ( 29) to drill drainage holes. One of the lifting units (1) has a container (21) for dispensing and collecting the beams (6).