And he didn't use a protractor to make those perfect letters or any other kind of measurements.

他没有使用量角器或任何他的测量方式来做出那些完美的字母。

Angles are usually measured using protractors.

角度通常用量角器进行测量。

Protractors have markings on them, similar to rulers, but instead of inches or centimeters it measures in degrees.

量角器上有何直尺类似的刻度，刻度不英寸或者厘米，而以度来衡量。

If you don't have a protractor to measure with, you can estimate how big it is as long as you remember what a 90 degree angle, 180 degree angle, and 360 degree angle look like.

如果你没有量角器，你可以估计它有多大，只要你记得 90 度角，180 度角和 360 度角什么样子的就行了。