Architects' and Engineers' Scale (the physical instrument)
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. It is typically multi-sided (three lobes in cross-section) and features multiple units of length and proportional length increments.
Part of Drafting Board
Part Type Entity
Screenshot Architects Scale.jpg

This is an architects' scale. It is not to be used as a straight-edge (for cutting), but rather only as an instrument to aid in producing drawings at scale .

When drafting architectural scaled drawings, the architect's scale is not used as a straight edge - it is only used to mark specific measurements. Over time and frequent use, scales can gather dents or have uneven edges, leaving drawings looking unprofessional if used as a straight drawing edge. Instead, use the parallel rule or a T-square and a set of drawing triangles to put lines onto the paper. This will maintain a consistent parallel line across your drawings.


Reading Architects' Scales
A video on how to read architect's scales found on, and by developed by R. Hewitt at the University of Memphis.