knife-cut recesses

Source reference: 

Pickwoad, The Interpretation... (1995)

Nicholas Pickwoad (1995), “The Interpretation of Bookbinding Structure: An examination of Sixteenth-Century Bindings in the Ramey Collection in the Pierpont Morgan Library”, The Library 17 (3), pp. 209–49.

Additional reference: 
p. 234

Used as preferred label for