The deckle is simply an open frame around the wire-covered mould; when the mould is lifted out of the vat, about a quarter of an inch of stuff is brought up and held in place by the deckle, so the water runs through the wires and the crossed fibres of the stuff remain on the wires to form the sheet of paper. The vat man's skilful shake of the mould causes a ripple to run across the wires at the moment the sheet of paper is made, as you can see in the photograph. Fibres seeping under the deckle gave the sheet a rough edge, often imitated in expensive modern papers. The weight of the stuff left marks that can be seen when the paper is held up to the light: wire lines, caused by the long wires; chain lines, caused by the heavier plaited wires across the mould; and the watermark, the paper maker's trade mark, twisted in wire and sewed to the mould. The vat man always had two moulds and one deckle in order to allow him to continue moulding while a boy or apprentice "couched" the paper onto a felt pad. When a sufficiently large "post" of wet sheets on felts had been built up, the whole output would be squeezed under a standing press.
