Frames and supports in 15th and 16th-century Southern Netherlandish painting

CHAPTER V 106 Fig. 58. Altarpiece closing systems. 1. Wooden cam swivelling on a nail. 2. Metal hook pivoting on a nail and entering a ring fixed in the corresponding stile (the mortises cut into the bottom side of the central part tell us that this was fixed with keys to a base). 3. Metal hook. The sides of the wings are rebated for tight closing (the round holes in the lower side tell us they were pegged to a base). 4. On closing, two pegs protruding from the side of one wing, fit into two notches in the side of the other wing. 5. A carefully rounded tongue enters a groove cut into the other wing. This latter system can be combined with the pegging described in 4. above. 6. Metal bolt. 7. Wooden batten with additional hook or bolt for closing. 8. Lock.