Dressed lumber is lumber that has been machine-finished and is smooth on all surfaces. Generally untreated wood is a better, safer choice to use for constructing indoor furniture such as playground equipment, lawn furniture or benches. Untreated lumber is the closest you will get to all-natural wood and is ideal for custom finishes like paint and stain or leave natural for a clean, simple look. They are lightweight and easy to nail, saw, trim or cut.