Steel plates, say of No. 14 gauge, are straightened or set by using a hammer andan iron setter. If, when the sheet is laid fiat, there are raised places along its centre, they must be worked down flat by hammering from the edge of the raised part outwards towards the edge of the sheet. If the centre of the sheet rests flat, and the edges are wavy, then the sheet is loose on the edge, and must be hammered from the wavy or loose parts in towards and along the centre of the sheet until the edges are drawn tight and true.