MDF stands for medium-density fiberboard and it is a material made from wood fibers. When pressed into a board for crafting it makes a very sturdy board that is fun for the whole family. Make into plaques or wall decorations. You can do anything you can imagine including painting and engraving. The boards have been well cut and have no rough edges so they are safe for creatives of all ages. These are for indoor use only and it is not recommended to hammer a nail into it. Each board measures 6 x 8 x 0.0785 inches.