Bookbinding - one form of join between the cover of a book and its spine.
A book with tight joints has its covers fastened flush with the turn-up of the spine. It is usually used in combination with a flexible spine. To make it easier to open the book, most covers with tight joints are chamfered along the spine side or nicked on the back corners.
closed
chamfered
board
|
V
__ ____________________________
/ |/ cover
/
|
|
| book block
|
|
\ _____________________________
\ |\ cover
open
_____
cover\
/ |
/
|
|
| book block
|
|
\ _____________________________
\ |\ cover
Note how the open book requires that the endpapers cover the ends of the cover boards and turn-up of the book block. There is a difficult balance between coverage and the additional bulk in the hinge that too much endpaper creates.
Tight joints are the traditional way of attaching covers to a book. They were supplanted by French grooves in the late 18th Century, but regained popularity along with flexible binding in the late 19th Century. It is still the preferred technique of the fine professional bookbinder.