Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Furnishings and Equipment (hierarchy name)
4. Tools and Equipment (hierarchy name)
5. equipment
6. [equipment by process]
7. image-making equipment
8. [equipment for drafting, drawing, and writing]
9. [drafting, drawing and writing equipment by general type]
10. drafting equipment
11. drafting instruments

Anotations

Scope note:

Instruments used to render perspective drawings. These consist of three rulers joined together in a Y-shape so that a central ruler, along which lines are to be drawn, may be orientated correctly by adjusting the position of the legs that rest against two nails placed on the drawing board. As the device pivots, the main bar changes slope, resulting in drawn lines that orient to a vanishing point that would be otherwise difficult to obtain.