In the case of revolving strainers, all that cannot pass through the slits falls to the bottom of the vat, in connection with which it is customary to have an auxiliary strainer, or “patent knotter,” as it is called, shown at E. All fibre that passes through this one, which is of the ordinary flat kind with shaking motion, goes into a box near E′, called the “low box” for “save-all” water (see p. 154). The pulp, after passing through the strainers, should be perfectly free from knots and impurities, and in a fit condition for making paper. In the machine shown, it passes from the last strainer directly on to the wire, its flow being regulated by a movable gate _e_. In some cases, however, it first flows into a small vat, in the centre of which revolves a rod carrying paddles, with the object of keeping the pulp well stirred up. It is carried right on to the wire by means of the apron, a piece of canvas, oil-cloth, or sheet rubber, one end of which is fastened to the breast-board _e′_, the other end resting on, and covering the wire to the extent of about 15 in. The edges of the apron are rolled up to prevent the pulp from overflowing. After leaving the apron, it passes under a gate, or “slicer,” as it is sometimes called, made of two pieces of brass, overlapping each other in the centre, and bolted together. It is made thus to enable it to be lengthened or shortened according to the width of the paper; its height from the wire-cloth can be altered by means of screws, and should be equal at all points, in order to ensure a uniformly thick sheet of paper. The ends of the two pieces forming the slicer are fastened to the frame _f_ or “deckle,” as it is called, and this again is carried by two or more rods stretching right across the wire, and fastened by small upright supports on both sides to the frame _g_. The deckle-frame also carries the grooved pulleys _h_, along which the deckle-straps _i_, endless square bands of indiarubber, move. {152} [Illustration: FIG. 49.] The object of the deckle-straps is to regulate the width of the paper; they form, together with the wire-cloth, a kind of mould into which the pulp flows, thus corresponding to the mould used in hand-made paper-making. The width of the paper can be altered by shifting the position of the frame _f_, and also the deckle-straps, which are carried on it as described, the pulleys _h_ being so arranged that they slide along the rods on which they revolve. In order to alter the width of the paper it is necessary to stop the flow of pulp on to the wire, and it not only consumes a considerable amount of time, but generally necessitates a partial cleaning up of the machine. Various attempts have, therefore, been made to devise an arrangement whereby the change can be effected while the paper is being made. Several {153} contrivances have lately been introduced, all similar to the one shown in Figs. 49 and 50.