There are three main ways to install wood flooring: glue down, nail down and floating. The method you choose should depend on where the floor is being installed, and over what type of subfloor. Traditional 3/4″ thick solid wood floors can be nailed or glued down over plywood, or glued down over concrete (not in a basement). Engineered wood floors can usually be nailed, glued, or floated over plywood or concrete, above or below grade.