hatching (techniques)

Preferred label: 

The technique of producing a series of fine closely laid parallel lines used to fill open tools or compartments in the tooled designs of bindings. Such tools are also known as azured tools.

AAT

The Arts and Architecture Thesaurus Online, The Getty Research Institute.

Additional reference: 
http://vocab.getty.edu/aat/300101921 (modified)
Broader concept: 
Broader partitive concept: 
Top concept: 
techniques
Getty AAT: