For marking the deviation indicating line on the ruler, hold the disc so that 0° is away from you and rotate the ruler so that its main body lies on the left hand side of the disc centre then screw in the direction between 0° and 180°.
Ukumaka isiphambuka esibonisa umgca kwirula, ubamba icwecwe ukwenzela ukuba u-0° ukude kuwe kwaye ujiealezise irula ukwenzela ukuba esona siqu sayo sihlale kwelona cala lasekhohlo lesandla esiphakathini secwecwe emva koko qinisa kweli cala liphakathi ko 0° kunye no-180°.