Page:Graphic methods for presenting facts (1914).djvu/254

 knobs from striking plastered walls can be placed at the top or bottom of alternate leaf surfaces. If these rubber bumpers are not available, a narrow strip of wood at the top and bottom of each leaf will serve.

When employed with glass-head pins having needle points, the drawer cabinets for maps used to route salesman, etc., can have a layer of cork composition fastened in the bottom of each drawer. The maps are then glued to the surface of the cork composition. The drawer cabinets regularly found on the market have sufficient drawer depth to permit placing a 3/8-inch layer of cork composition in the bottom of each of the regular drawers and still allow room for the pins. Map pins may be pushed into the cork composition so securely that no pin will ever be misplaced even if a book or other heavy object should happen to drop upon the map and the map pins. Pins in cork composition are so easily inserted and removed that they can be handled more rapidly than if stuck into any kind of a board surface. When ordering maps from any map manufacturer or map store for use with glass-head pins care must be taken to specify either a cork-composition backing or a corrugated straw-board backing, else the map will probably be shipped mounted on compo-board or some other surface entirely too dense to permit of pushing the map pins in until the heads touch the surface of the map.

If numerous glass-head pins are to be put into a map at one time, the eraser in the end of a lead-pencil should be used to push the pins down until the heads touch the map. Pins can be very quickly located if only their points are pushed into the map by hand, leaving the main pressure to be applied by the lead-pencil eraser after a number of pins have been located. The pencil-eraser method saves time and it also eliminates the discomfort which may be caused if thousands of pins are pushed into a map by using the thumb and forefinger only.

Line cuts, sometimes called zinc cuts, may be made directly from pin maps if glass-head map pins of suitable color are used. At the point on the map where each pin head is located there will be a black dot on the print made from the zinc cut. As light is reflected from the surface of the glass heads of the pins, there are sometimes shown in a photograph high lights which must be retouched with a pen or a fine brush so that the whole spot shall be black, rather than black with a white center, as seen in Fig. 191. Anybody can do this retouching very quickly. It is mentioned here only as a caution that the photograph be inspected before the zinc engraving is made from it.