Rulers, also known as rules, began as an attempt to standardize measurements based on the human anatomy, such as the foot and the hand. By the 17th century, rulers were marked in inches, with smaller, fractional lengths coming later.
From the start, the impracticality of very long rulers was obvious, so carpenters and tool makers alike devised ways to fold their wooden rulers so the tool would be easy to store and move from job to job. Rules that folded in half, thirds, and quarters were common. Stanley made a zig-zag rule that was hinged in brass in 15 places, while interlocking rulers allowed carpenters to take inside measurements.
Another type of ruler favored by carpenters was the combination rule, which could include a level, inclinometer, square, or compass into its design. Framing squares and combination squares, which usually had metal blades and wooden handles made of cherry or other hard woods, were typically marked on their blades to at least a sixteenth of an inch...
More specialized types of rulers include rules used by lumbermen and loggers. Cruising sticks helped foresters calculate the amount of board feet in a standing uncut tree, while log rules calculated board feet in a cut log. Board rules helped the lumberman determine board feet in a sawn board.
In general, early lumber rules were made only of wood, but later models added a rounded or oval brass tab at one end and a handle at the other, to save the lumberman the trouble of reaching out to the end of whatever he was measuring to make sure the rule was flush with its outer edge.
Other specialized rulers included patternmaker’s rules, which were also known as shrinkage rules since they helped foundry workers account for the shrinkage that would occur when casting metal. Using this rule, a wooden mold could be made slightly larger than the finished product being cast, depending on the shrinkage rate of the metal.
Caliper rules measured the thicknesses of rope and cable (some rulers had a caliper built into one of their ends), while navigational rules helped sailors and mapmakers. One rule that is closely associated with navigation but is not really a rule at all is the parallel rule, which was used to draw parallel lines. Often made of ebony or blackened boxwood, these rules had a pair of metal hinges between them so that parallel lines of varying distances apart could be drawn accurately.
While most rules produced by Chapin-Stephens, Lufkin, and Stanley were made of woods such as boxwood, some were made of bone and others were even carved from ivory, with hinges and fittings made of an alloy called German silver. These ivory rulers are among the most expensive available to tool collectors today, even those whose ivory has yellowed with age.