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Set square (IS:1361-1988): Transparent celluloid /Plastic setsquares are preferred and are commonly used rather ebonite ones. They are two in number, each having one corner with 90°. The setsquare with 60°-30° of 250 mm long and 45° of 200mm long is convenient for use. Setsquares sometimes loose their accuracy due to internal strains. So they should be tested periodically

Sometimes set squares have french curves. Set squares are used to draw all straight lines except horizontal lines. It is convenient to draw horizontal lines using Mini drafter.

Scales: Scales are used to transfer and or to measure the dimensions. They are made of wood, steel, ivory, celluloid or plastic, stainless steel scales are more durable. different types of scales used are shown in Figs 1,2 & 3. They are either flat, bevel edged or triangular cross-section. Scales of 15 cm long, 2 cm wide or 30 cm long 3.5 cm wide flat scales are in general use. Thin section or bevel edged scales are preferred over thick flat scales. Parallax error will be nil or least while using thin / tapered edge scales

Protractor: Protractor is an instrument for measuring angles. It is semi-circular or circular in shapes and is made of flat celluoid sheet. 

The angles can be set or measured from both sides, aligning the reference line and point ‘0’ with the corner point of the angle.

Figure  shows how to read or set the angle. Protractor can also be used to divide a circle or drawing sectors.