Scale ruler

A scale ruler is a tool for measuring lengths and transferring measurements at a fixed ratio of length; two common examples are an architect's scale and engineer's scale. In scientific and engineering terminology, a device to measure linear distance and create proportional linear measurements is called a scale. A device for drawing straight lines is a straight edge or ruler. In common usage both are referred to as a ruler.

An architect's scale is a specialized ruler designed to facilitate the drafting and measuring of architectural drawings, such as floor plans and orthographic projections.

Because the scale of such drawings are often smaller than life-size, an architect's scale features multiple units of length and proportional length increments.
 

For accuracy and longevity, the material used should be dimensionally stable and durable. Scales were traditionally made of wood, but today they are usually made of rigid plastic or aluminium. Architect's scales may be flat, with 4 scales, or have a symmetric 3-lobed cross-section, with 6 scales.
 

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