Toothing: the bricks that stick out for later

In ordinary English, toothing refers to notching or serrating a surface, the way a saw has teeth. The verb "to tooth" means to create a toothed edge or pattern, and you might tooth a joint in woodworking or metalworking to lock two pieces together mechanically.

In construction, a toothed wall is built with exactly the opposite intention: instead of cutting away material, bricklayers project bricks outward at regular intervals. The definition calls these alternately projecting bricks at the end of a wall. This means every other brick (or every other course, depending on the bond pattern) is left sticking out beyond the face of the wall by roughly half a brick's depth.

A builder uses toothing when a wall is temporary or when its completion will be delayed. By leaving toothed bricks projecting, the mason creates mechanical anchors. When work resumes and the remaining section of wall is built up to height, fresh mortar bonds those projecting bricks directly into the new work. The result is a seamless junction, as if the entire wall had been laid continuously. Without toothing, a wall built against a flat vertical surface would need a separate mechanical tie or would risk a weak vertical joint.

The term borrows from the visible analogy: just as teeth protrude from a jaw in a regular pattern, so do the toothed bricks protrude from the wall face in a regular sequence. The word applies the same logic of mechanical interlocking that a saw's teeth use to grip wood, except here the interlocking is between the old work and the new work, and it happens through mortar and stone instead of friction and pressure.