loose pagesHinging-in is generally used when the text block is sewn and the pages open flat, or when reattaching a plate that was originally tipped onto a page in the text block.There is a description of sewn text blocks and how they are constructed in a previous post.

A detached page can be hinged to the page in front or in back of it. While each mend should be evaluated individually, the strongest mend is usually accomplished by hinging from the back of the detached page to the front of the page immediately behind it. That way, the Japanese repair tissue will support the page underneath as it is turned.

Each signature of paper is made of folios (single folded sheets) and each folio is made of 2 leaves (one single 2 sided page). When one leaf is detached, always check that its other half is still well attached to the text block. The other half might still be held in place by the original glue, or it might also be loose.
1. Check the attachment of the second half of a folio by finding the center of the signature with the detached page. Look for the sewing threads at the center of the signature and mark the center with a slip of paper.
2. Count from that center toward the detached page, then go back to the
marker at the center of the signature and count the same number of pages in the opposite direction. That should be the other half of the folio.
3. If the other half of the detached page is still firmly attached to the text block, hinge in the detached page using the technique outlined in the post Hinging In a Single Page.
4. If the other half of the detached page is also detached or loosely attached, both halves must be reattached.
5. If the spine of the text block is accessible, use the instructions in the post Reattaching a Separated Signature Page to reattach both pages.

Detailed instructions for the techniques required for hinging-in are in the next few posts.