coign

Coign is a term used in architecture and woodworking to describe a projected angle or corner, often formed by intersecting beams or walls. It refers specifically to the supportive or decorative element that reinforces the integrity of an angle, providing both structural strength and aesthetic detail. In many timber-framed buildings, coigns are visible where two joists or rafters meet, and they may be shaped or carved to add visual interest or to accommodate a particular joint form.

The word derives from the Old French "coign," meaning "corner," and it entered Middle English in the 14th century. Its use has historically been associated with timber framing, stone masonry, and shipbuilding, where precision in angled joints is essential. In carpentry, a coign can be a simple square notch or a more elaborate mortise-and-tenon joint that locks two beams together. In artillery, the term also appears as "coign of armor," describing angled panels on a shield or armor plate designed to deflect blows.

In modern construction, coigns are often included in the design of lath and plaster or drywall corners to manage stress and prevent cracking. Decorative coigns are sometimes used in kitchens and bathrooms where corners of cabinets or tiles are exposed. While largely a technical term, it is still employed by architects and builders when detailing joints that require special attention to angles.