tongue and groove 
noun [mass noun]
Wooden planking in which adjacent boards are joined by means of interlocking ridges and hollows down their sides: he’d built units in tongue and groove [as modifier]: tongue-and-groove panelling...
- If plywood is impractical, 1x6 tongue and groove boards may prove to be an easier solution.
- Finally, insulate the cavities and then install sheets of tongue and groove plywood subfloor, using adhesive along with your fasteners.
- The material comes in individual boards with tongue and groove edges, roughly eight inches wide by four feet long.
Derivatives
tongued-and-grooved
- Nailing ceilings, one nails a wood tongued-and-grooved board in place while standing on planks laid across sawhorses.
- Then there's the tongued-and-grooved joints, which enable the panels to fit tightly together.
- According to the invention, the edges of the tongued-and-grooved block are bevelled such as to produce a trapezoidal form which can be used to facilitate the positioning of the block, and to adjust the block.