In using the notched-card scheme two notches may, if desired, be placed in the top of each card, thus permitting many more group combinations than would be possible if only one notch were used. The notches may be cut with a special instrument of rather simple construction so as to insure their uniform spacing right or left from the upper corners of the card. A notch in the form of a segment of a circle is the most satisfactory.

In order to keep the general rule that original curve cards shall not be taken out of the record room, it is well to provide means by which blue prints can be made quickly from any curve card. In a business of reasonable size, blue prints may easily be made with a small-size printing frame and sunlight printing, if the record room is located on the southern side of the building where there is sunlight most of the time. In large businesses electric blue-printing machines are a part of the regular equipment of the drafting office. If the drafting office is not near the record room, however, it may be well to equip the record room with an electric blue-printing machine and a small washing tank, so that blue prints of each card may be made without the necessity of taking confidential record cards out of the room. Photographic processes for copying records have recently been much improved. A machine called the photostat makes black and white copies quickly without the expense of glass negatives. With a blue-print machine or