The slide rule is a rather simple machine to look at and consists of very few moving parts.  The picture below highlights the main parts of any slide rule.

Nestler Nr. 0130 MultiMath-Duplex

The basic slide rule is made up of the upper and lower stators which make the body of the rule.  These are held together by moulded or metal brackets to give stability.  Between runs the slider which can be removed from the rule and reversed if necessary or appropriate.  Along the body of the rule runs a clear cursor and within the cursor is at least one hairline used to help align values and read results.

Along the body and slider are a series of scales used for different purposes.  Whatever scales are present depends on the purpose of the slide rule itself; many were designed for a specific purpose whereas others are more general.  Whatever slide rule you own, you will always find the C and D scales present and these are the two most commonly used scales.

Not all slide rules are duplex, i.e. have scales on the front and back.  In fact many of the non-duplex slide rules had rules, constants and unit conversions on the back.  For some companies, it was not uncommon to include a separate rule which would have a variety of constants, conversion and scales for measuring lengths, like the traditional rule.

The most important feature is the scale, which we will consider under the Geometry of a Slide Rule.