Scale ruler

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

In the United States, and prior to metrication in Britain, Canada and Australasia, architect's scales are marked as a ratio of x inches-to-the-foot (typically written as x″=1′-0″).

It is commonly made of plastic or aluminum and is just over 300 millimetres (12 in) long, but with the only 300  mm of markings, leaving the ends unmarked so that the first and last measuring ticks do not wear off.

It is used in making engineering drawings, commonly called blueprints, blue lines, or plans on a specific scale.

[2] Typically in civil engineering applications, 1:10 (1″=10′) is used exclusively for detail drawings.