Different rules for different rulers
When it comes to rulers, some people are experts. This doesn’t mean that everyone knows how to utilize them properly. The reality is that some types of rulers are not the easiest to use, and there are many types: for children, angle, square, standard, and a protractor.
The first ones are those shaped to underline; often, they come in different designs to make them more fun to look at. Square, protractor, and angle are types of rulers used for geometry. But when measuring, keep an eraser nearby in case of mistakes, like what is seen in the image.