Wire-O™ binding, also called wire binding and Double-O binding, is a method for binding documents. This binding method is inexpensive and is typically used in North America for binding things like books, booklets, calendars, spirals, day planners and other small readers.

There are a few things to know about Wire-O™ binding before purchasing a machine or having something bound. To bind a book using the Wire-O™ binding method, the document is placed into the machine and holes are punched into one side, similar to a large three-hole punch. Some binding machines punch three holes per inch (2.5 cm), and others punch two holes per inch. These are called pitch ratios and are referred to as either a 2:1 Pitch or a 3:1 Pitch. The holes punched can be square, round, or rectangular, but are most often round.

If the Wire-O™ binding machine is a personal-use apparatus and the document to be bound is large, the machine may not be able to punch through all of the pages in the document at once. To combat this, users typically break the document up into smaller sections and punch through those sections one at a time.

After the pages have been hole-punched in the Wire-O™ binding machine, they are removed and a C-shaped spine is placed into the device. The spine is made of flexible wire. The punched pages are placed in numerical order over one end of the C-shaped spine while the spine is sitting in the Wire-O™ binding machine.

If the machine being used is an at-home machine, the user then manually closes the C-shaped spine, reshaping the spine into an "O" and effectively binding the document together. The spine is typically closed by pulling a lever. For larger, more commercial machines, most of the binding process is done automatically. After a document is bound using this process, it can be placed flat on a table top or opened 360 degrees.

Another binding method that is similar to Wire-O™ binding but not commonly used anymore is called 19-loop wire, which was designed to be used with a comb binding machine rather than a wire binding machine. The company who distributed these 19-loop wires was bought out, and the product was discontinued. The method has since fallen out of ordinary use. This type of binding was typically called Spiral-O binding.

Wire-O™ binding is common and goes by several other names. In addition to Wire-O™ binding, wire binding and double-o binding, the process can also be called wirebind, twin loop wire, ringwire and double loop wire. Machines for personal use are easily found and can be purchased online through several companies or at office supply stores.

Personal binding machines are typically manual and small enough to fit on a desk top. Larger binding machines are often purchased for company use when the documents to be bound are larger in size and greater quantities of them are distributed. These can also be found online for purchase, and are generally electric and work faster than manual machines.