On some days all the orders for one commodity might be small orders, and on the next day a very large quantity of that same commodity might be handled all in one large order, so that a gang of men could work steadily all day on that one order. Naturally if a large gang of men work all day on one order, the cost per package handled would be very much less than if several different gangs were used in handling numerous orders of only ten or twenty-five packages each. In order to get a clear view of what was actually happening, considerable study was given to the problem and the method shown in Fig. 159 is the result.

It was decided to make a pin board about 24 by 30 inches, on the general scheme seen in Fig. 159, by which separate orders could be shown on the chart by a dot to represent each order handled. As it was desired to keep continuous records for the chief commodities, it was not feasible to make ink marks for it would then be necessary to start over again frequently with a completely new sheet of paper. To overcome this difficulty, short pins were used having spherical glass heads only ^32 inch in diameter like those seen at the right in Fig. 186. The co-ordinate paper for the chart itself was mounted on three layers of corrugated straw-board, having the ribs of the middle layer at right angles to the ribs of the two outside layers, as described in Chapter XII. A binding of gummed cloth -tape around the edge of the board gave a neat appearance and assisted to preserve the boards during rough service and long use. These boards were very light, yet remarkably strong on account of the corrugations running in both directions.