This type of joint is called a dado. Tongue and groove boards can be used for many things, such as walls, ceilings, flooring, ...
and achieving the stiffening of the structure Floor-to-ceiling format for maximum flexibility in construction Optimized tongue and groove profile for secure and precise installation Important ...
Nails hold tongue-and-groove ceiling boards to the ceiling joists. The nails go through the tongue side of the board, and then the groove side of the next board goes over the tongue. This unique ...