[Tom Edgerton]

I just built a house, and we used some MDF.

My basic conception of it is that Masonite is a very hard board made of cellulose fibers and glue. Tempered Masonite is very hard and almost glossy on one side. Untempered Masonite is more porous on the flat side, not as glossy, but still pretty hard.

MDF, while made a similar way, isn't as dense throughout as Masonite, and generally has a separate "skin" laminated to it all around. It comes in boards and sheets. I don't know if you can get MDF as thin as a quarter- or eighth-inch sheet, like the Masonite.

MDF works up very well, and takes paint well, and it is uniform throughout and isn't supposed to warp. But it is bloody heavy compared to wood or Masonite, in spite of its name. It's great for shelves.

Michele is right in that Masonite is a brand of hardboard, and MDF is a generic term for Medium Density Fiberboard.

We also used something called MDO (Medium Density Overlay) in the bathroom, which is supposed to be more waterproof. But I can't really tell you the difference in how it's made.

The guys at a good building supply dealership could probably make this a lot simpler explanation than I have.

A little knowledge....as they say.