Scales are either engine divided or stenciled/painted. Engine division is
highly accurate and etched into the scale face. Stenciled or painted
increments are less accurate and easily worn away.
A DM must know four terms relating to the way in which increments are
displayed on a scale that a DM must know. These are open divided, fully
divided, double numbered, and single numbered.
OPEN DIVIDED: On an open divided scale, only the main increments are
shown. There is one fully subdivided increment on the end of the scale to
the left of the 0 point, Measurements of full units are read from the right of
the 0, while partial increments are left of the 0.
FULLY DIVIDED: All increments on a fully divided scale are shown. This
makes it easier to use, but not easier to read.
DOUBLE NUMBERED: The convenience of a double-numbered scale are
that it reads from left to right and from right to left, allowing two different
scales to appear on the same scale face.
SINGLE NUMBERED: This is by far the easiest scale division to read
because there is only one scale per face, and it is usually fully divided.
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