Indiana University Libraries Book Repair Manual

Rulers

We chiefly use the metric system of measure. Metric rulers are a bit more precise than rulers marked off in inches, as the units of measure (millimeters) are slightly smaller than those of our conventional Western rulers (most commonly sixteenths of inches). But the main advantage lies in the fact that the metric system of measure is in base 10, rather than the base 12 of inches. With a little experience, the metric measuring system becomes quite easy and handy to use.

The terms "ruler" and "straight edge" simply refer to whether or not (respectively) the tool is marked for measuring. So, the image shows a straight edge on the far left; the rest are rulers.

The straight edge on the far left and the ruler on the far right are both 1 inch (2.5 cm) wide. As you will see throughout the manual, these get used a lot for trimming cloth to a 1" turn-in.