The Manuscript Codex * Structure

The passage of thread through the gatherings in order to connect them and thus form the textblock. Usually, the thread passes through the spine-folds of the gatherings, but may connect stacks of loose leaves in a different manner.
# Without any qualifier, the sewing always refers to the primary linkage of the gatherings along their spine-folds. However, there is also another type of sewing, the sewing of the primary endband. Once this type of sewing has been qualified by an initial reference to the endband, subsequent uses of the phrase can drop the qualifier and refer to this, too, as simply the sewing. The same can also be encountered with the sewing of the secondary endband. This is even more confusing because, in fact, the secondary endband is actually woven and not sewn.
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UBL OR. 502