Angles are usually measured using protractors.

角度通常用角器进行。

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

没有使用角器或任何方式来做出那些完美字母。

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

角器上有何直尺类似刻度，但是刻度不是英寸或者是厘米，而是以度来衡。

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 度角是什么样子就行了。