Tongue and Groove Solid wood planks are equipped with a sturdy and efficient tongue and groove system that ensures a strong and long lasting joint whether glue or nail down installation is used. As the tongue is made of the same material as the rest of the plank, it ensures not only the structural integrity of the plank but also that irrespective of the set up method, the floors will maintain their appearance in time.     In the case of nail down installations, special bail guns are used to release nails at a 45 degree angle so that it penetrates the tongue and secures the plank to the sub floor. The groove side of the next plank acts as a seal for the head of the nails as they are hidden but also ensures that the planks are not just fixed to the floor but to each other as well.     For glue down installations the function of the tongue and groove system is the same as it ensures that the planks are securely fixed to one another when they are glued directly to the floor.