Notes - Do not use fibre board! I used MDF to make these box bellows. I used several layers of paint, but after a few years moisture did manage to warp my box all over. Also, it was way to heavy because of the MDF (actually, some weight is good to keep it in place while you are working it at the forge). - Make it smaller! When working the bellows I do not use the full metre length anyway, as the piston is harder to move in a straight line when most of the piston length is out of the box. And I think it's better for the forge fire anyway to be able to provide a steady source of air instead of bigger volumes in less steady amounts.