The protractor makes half a circle with a 7 centimeter radius. In the middle of the straight side a 2 centimeter wide semi-circular hole has been made, to fix the protractor on a line, or combine it with the ruler or a knob. On the round side, per ten degrees there is a little point as indication. In the round edge it also has small notches, for precisely placing the pen. Little slots on the top suface indicate the 30, 45, 60 and 90 degrees angles.
There are round holes of 0.5, 1, 1.5, 2 and 2.5 centimeters in diameter, to easily draw circles this big.