Tongue and Groove
One side and one end of the plank have a groove, the other side and end have a tongue (protruding wood along an edge’s center). The tongue and groove fit snugly together, thus joining or aligning the planks, and are not visible once joined. Tongue-and-groove flooring can be installed by glue-down (both engineered and solid), floating (mostly engineered only), or nail-down (not recommended for most engineered).
or Woodloc systems: there are a number of patented “click” systems that now exist. A click-in floor is similar to tongue-and-groove, but instead of fitting directly into the groove, the board must be angled or “tapped” in to make the curved or barbed tongue fit into the modified groove. No adhesive is used when installing a click floor, making board replacement easier. This system not only exists for engineered wood floors but also engineered bamboo and a small number of solid floors and is designed to be used for floating installations. It is beneficial for the Do-It-Yourself market.
Wood flooring can also be installed utilizing the glue-down method. This is an especially popular method for solid wood flooring installations on concrete sub-floors. Additionally, engineered wood flooring may use the glue-down method as well. A layer of wood floor adhesive is spread evenlly onto the sub-floor using a trowel similar to those used in laying ceramic tile. The wood pieces are then laid on top of the glue and hammered into place using a rubber mallet and a protected 2×4 to create a level floor.
A floating installation is where the flooring is laid down in a glueless manner on top of a layer of underlay. The individual planks are locked together, and are not glued or nailed down to the subfloor. By doing this the floor is floating above the underlay, and can be laid on top of existing tile or marble, without the risk of damaging the subflooring.