The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Examples from the Web for head cap
The edges of the boards may have a gold line run on them, and the head-cap may be decorated with a few dots.Bookbinding, and the Care of Books|Douglas Cockerell
The usual method of removing a book from the shelf is to hook a finger into the top of the back, or head-cap, and pull.Book Repair and Restoration|Mitchell Buck