Circleometers and ellipsometers

Drawing templates, circle gauges, curved ellipsometers and other geometric figures are used when the standard graphic element must be drawn “by hand” repeatedly. A drafting template is a flat piece of plastic with the standard symbols cut out inside. Drafting templates and architectural figures are used as a guide for drawing symbols of various types on the project. Templates exist for different scales of representation.
Drafting templates are also available for a range of floor plans and elevation/prospect systems. There are many symbols that can be represented by a template, furniture, doors, windows, taps, electrical devices, urban planning symbols, etc. etc.

The curvilinear It is a small set square made of plastic, wood or metal used in manual drawing to trace various types of curves of variable radius.
Curve models were decisively developed by the German mathematician Ludwig Burmester (1840-1927). In its function it has now been largely replaced by computer-aided design (CAD) programs, but it is still used in educational institutions.

In the image, the first model is used mainly to help the designer in drawing hyperbolas; the second mainly for ellipses.
Another method for tracing special curves is to use a flexible strip that is held in place on the drawing. This method was used especially in naval drawing for tracing the starting lines of the hulls.

Another method is to use a deformable rod that is shaped as needed; however, after being used several times, these rods remain more or less wavy, thus becoming unusable. 

Some content on this page was taken from: https://it.wikipedia.org/wiki/Curvilineo

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