For the inner walls and divisions, iron in various forms is to be recommended; for it is non-absorbent, non-inflammable, and is stronger, more durable, and occupies less space than any other substance in ordinary use; but is more expensive. Iron divisions, doors, posts, and other fittings can be bought ready made; the only addition required being wood panels for the lower part of the divisions (partitions) of the stalls and boxes. Bricks take up a great deal of room for obtaining sufficient thickness. Wood, on account of its cheapness, is largely used for divisions. An objection to wood as a material for divisions and doors of stalls and boxes, is that horses are as a rule much inclined to gnaw it. This disadvantage can be easily obviated by placing a protective covering (strips of sheet-iron, for instance) over the wood. Elm is one of the woods least open to this objection. Horses are particularly fond of using their teeth on deal.