outer joint
The grooves in the covering material at which the
boards open. Also called (outer) hinge. The term
"joint" is sometimes used to indicate the ridge or
abutment formed by the backing operation to
accommodate the boards; however, this ridge is
more appropriately referred to as theSHOULDER(S) (1) of
the book. See also: FRENCH JOINT . (237 )
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