The scales are the brains of the slide rule you might say.  Each scale is used for a specific purpose and generally works in conjunction with one or two other scales.  There are quite a few scales that can appear on different slide rules and you will not find one slide rule that possesses all scales (it would be significantly large and awkward to use).

This section is only used to introduce the more common scales, not to show their operation, this will be done in later sections.  Links will be supplied for you to investigate other scales which have appeared on some slide rules from time to time.