The rolled-plate annealing kiln is essentially a long, low tunnel, kept hot at one end, where the freshly-rolled sheets are introduced, and cold at the other end, the temperature decreasing uniformly down the length of the tunnel. The sheets pass down this tunnel at a slow rate, and are thus gradually cooled and annealed sufficiently to undergo the necessary operations of cutting, etc. Although thus simple in principle, the proper design and working of these “lears” is by no means simple or easy, since success depends upon the correct adjustment of temperatures throughout the length of the tunnel and a proper rate of movement of the sheets, while the manner of handling and supporting the sheets is vital to their remaining flat and unbroken. The actual movement of the sheets is effected by a system of moving grids which run longitudinally down the tunnel. The sheets ordinarily lie flat upon the stone slabs that form the floor of the tunnel, and the grids are lowered into recesses cut to receive them. At regular intervals the iron grid bars are raised just sufficiently to lift the sheets from the bed of the kiln, and are then moved longitudinally a short distance, carrying the sheets forward with them and immediately afterwards again depositing them on the stone bed. The grids return to their former position while lowered into their recesses below the level of the kiln bed. When they emerge from the annealing kiln or “lear” the sheets of rolled plate-glass are carried to the cutting and sorting room. Here the sheets are trimmed and cut to size. The edges of the sheets as they leave the rolling table are somewhat irregular, and sometimes a little “beaded,” while the ends are always very irregular. Ends and edges are therefore cut square or “trimmed” by the aid of the cutting diamond. For this purpose the sheet is laid upon a flat table, the smoothest side of the sheet being placed upwards, and long cuts are taken with a diamond--good diamonds of adequate size and skilful operators being necessary to ensure good cutting on such thick glass over long lengths. Strips of glass six or eight feet long and half an inch wide are frequently detached in the course of this operation, and the final separation is aided by slight tapping of the underside of the glass just below the cut and--if necessary--by breaking the strip off by the aid of suitable tongs.