To make a cylinder, first draw a circle on the paper, then cut out two identical circles, and then calculate the circumference of the circle (the length of the side development diagram of the cylinder). Due to the influence of paper thickness, it needs to be pasted when making, so the length is longer when you see the side spread diagram.

Cut it off first. Remember not to cut the part connected with the rectangle. Fold the serrated part inward, apply glue, roll up the rectangle, and stick the serrated part on the inside of the rectangular paper tube.