Screen angle indicator: A protractor with many co-centre circles. When placed over a half-tone film or print, indicates by a halo, the screen angle of the half-tone.

• 网角指示器:是一个带有很多同心圆的量角器。把它放在瘗半色调底片上，现出圆晕，指出该半色调的绸线角度。