The mortise and tenon is a joint between timber members: one end is cut into a projecting tenon, the other is chiselled into a hollow mortise, and the two fit together so that two pieces of wood become one. Common forms include the dovetail tenon, the half tenon and the through tenon.
Wood is tough, and the tenon and mortise must be worked to a close fit for the members to grip. A little room is left between tenon and mortise, so when a building sways the members can shift slightly and then partly return. A joint like this gives timber buildings some resistance to earthquakes.
Close work also needs a common measure. In the Northern Song Li Jie compiled the Treatise on Architectural Methods, which set the sizes of joints and members in major timberwork by the cai-fen units, so that craftsmen cut timber and tenons to one set of proportions.
Mortise-and-tenon building is a timber construction technique in which a projecting tenon fits into a hollow mortise to join beams, columns and other members. This way of joining wood already appears in Neolithic pile dwellings, was written into Li Jie's Treatise on Architectural Methods in the Northern Song, and in the Ming was used to raise the palace halls of the Forbidden City.
