The line of chords scale rule incorporates a scale from 0 to 120 in 12 increments two centre dots are provided one on each blade and with the aid of dividers the rule can be set at any angle or an existing angle can be determined line of chords the circumference scale indicates the circumference by measuring the diameter packed in display wallet600mm 24 in length sub divided mm and line of chords scale one side sub divided mm and circumference scale in mm other side