Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

overcasting

A method of hand sewing in which groups of single sheets are sewn together using a single length of thread which passes through the paper and over the back edges of the leaves. Overcasting is sometimes used when sewing a book made up of single sheets, the "sections" created being sewn flexibly. It is also a method used by library binders when attaching new endpapers to a book being recased, or to reinforce the first and last sections of a book being rebound without resewing.

Overcasting is a strong form of sewing, but it results in considerable strain on the leaves and frequently cuts the paper, partly because of the diagonal at which the thread passes through the paper. In addition, when groups of leaves are overcast and then sewn on cords or tapes, unsightly gaps are seen between the "sections." (84 )