c/12 diagonal is a diagonal speed that is equivalent to one twelfth of the speed of light.
Dean Hickerson found the first c/12 diagonal spaceship in April 1991. It was named the Cordership to honour Charles Corderman, who discovered the switch engine, the basis for all Corderships. It was noted by Corderman that the switch engine travels diagonally at c/12 with a period of 96, before it is destroyed by its own debris. To create the first Cordership, the 13-engine Cordership, Hickerson put thirteen switch engines together so that they canceled out their own debris. Hickerson soon created a smaller Cordership, the 10-engine Cordership, and later found Corderships that used 7 and 6 switch engines. Currently, the smallest known Cordership is the 4-engine Cordership, found by David Bell on July 9, 2005, although a slightly larger Cordership using only three switch engines was found by Paul Tooke on January 12, 2004.
The structure of Corderships makes them easily manipulated, and they can participate in a large number of reactions, such as turning or duplicating gliders. The Cordership's versatility has made it ideal for many patterns with special properties, such as Sawtooth 260 and the infinite glider hotel. Corderships of higher periods can also be created using a variety of techniques; however, Corderships must have a period that is a multiple of 96, due to the switch engines movement.
The first c/12 diagonally traveling patterns to be found were puffers found by Charles Corderman in 1971, the block-laying switch engine and glider-producing switch engine, which have periods of 288 and 384 respectively. Corderman found that these patterns could arise from a switch engine's interaction with a block, resulting in some small infinite growth patterns with only 11 cells. There are now known infinite growth patterns with only 10 cells, but they all end up producing a switch engine. These puffers can be easily constructed, and so they often are the basis of small quadratic growth patterns, such as in Nick Gotts' 26-cell quadratic growth pattern. Several other c/12 diagonal puffers have been created using multiple switch engines which stabilize each other.
Due to the versatility of Corderships, rakes are relatively easy to create, and various methods have been designed to increase rake periods.
The only known c/12 diagonal wickstretchers are line stretchers which stretch a canoe using a glider synthesis. This led to the creation of an adjustable period spaceship in which the line of a line strethcer is broken by a following spaceship, causing a fuse burn up the line until it reaches the building component of the spaceship, at which point the fuse will stop burning and allow the following ship to repeat the process.
Due to the fact that switch engines are easy to synthesize, many glider syntheses have been made for Corderships, resulting in the creation of several guns which shoot c/12 diagonal spaceships; notable examples of this are the v-gun, the 6-engine Cordership gun, and the 3-engine Cordership gun.