A means of fastening sheets of paper together using metal or plastic attachments inserted through punched or drilled holes in the paper. Ironically, of the four major methods of binding, "mechanical" binding is the least mechanized. There are three primary types of mechanical binding:
'Loose-Leaf Binding'. Loose-leaf binding is the simplest and most common form of mechanical binding. In one variety, pages are placed in a book, or binder, and held together by means of a metal clamp. In others, plastic strips also serve as clamps to hold pages together. Slightly more elaborate types of loose-leaf bindings are the popular ring binders (most often found in a three-ring variety). Metal rings mounted inside the binder can be fitted through holes punched or drilled in the sheets. Ring binders (and similar post binders) have the advantage of allowing sheets to be inserted or removed easily, which makes them well-suited for publications, presentations, and other such documents which will be updated with some degree of frequency. The holes can be punched prior to printing (some letter-size paper is sold pre-drilled) or afterward, either by a professional bindery or using a hand-held hole-punch widely available at office supply stores.
'Spiral Binding'. In spiral binding, a long series of small holes is punched or drilled along the length of the binding edge, and a continuous wire or plastic coil is threaded through the holes. The ends of the coil are then crimped, and the pages within are secure and can be opened flat. Spiral binding is often used for notebooks, cook books, instruction manuals, or other types of publications that need to remain flat when opened. Wire-O binding is one variety of spiral binding.
'Comb Binding'. Comb bindings consist of a strip of solid plastic with curved teeth or prongs extending off it. These prongs can be inserted into slits drilled or punched into the binding edge of the sheets. Comb bindings have the same advantages as spiral bindings, an added advantage being that there are no crimped wires to come uncrimped and slowly unravel, an occasional problem with some heavily-used spiral-bound notebooks.
In spiral and comb binding, covers can be added to the top and bottom. In loose-leaf binding, the binder itself acts as a cover, and some loose-leaf binders allow for cover sheets to be inserted into clear plastic pockets on the front of the binder.
Mechanical binding is inexpensive, but used primarily on very short-run jobs and/or internal documents and publications.