The folded edge at the head, tail, or fore edge of a section of an unopened book. Depending on location, it is known as a head bolt, tail bolt, or fore-edge bolt. Bolts are generally located at the head and/or fore-edge, but cannot be located at all three edges on any one leaf. The folded edge opposite the fore-edge is not a "bolt", but a spine-fold. Bolts are often opened quickly and with little care, resulting in ragged edges that are difficult to handle when turning leaves. A dull knife used carefully will result in a clean cut, while a knife that is too sharp is difficult to control and often cuts away from the bolt and into one or more leaves.
bretter i papiret som oppstår når trykkarkene falses til legg og som må sprettes eller skjæres opp for at boken skal kunne åpnes