Set square

The simplest form of set square is a triangular piece of transparent plastic (or formerly of polished wood) with the centre removed.

In some European countries a common form of set square combines a 90-45-45 triangle, a ruler and a protractor into a single tool made of stiff or slightly flexible transparent plastic.

[1][2][3] Being a mandatory tool used by pupils in middle school and higher in German-speaking and neighbouring countries, this specific design is named "Geodreieck [de]" (short form of "Geometrie-Dreieck", meaning "geometry triangle") or similar.

[3] It was originally developed in 1964 by the German manufacturer Dennert & Pape Aristo-Werke [de] (after several refirmations now Geotec Schul- und Bürowaren GmbH).

[3] Variants in larger sizes, with fixed or detachable handles, with or without bevelled edges (facets), and with or without ink nodules or embossed labels exist as well.