How to draw a line on the crescent mouth of a circular tube

1. First, flatten one end of the round pipe, draw a straight line on the board with a ruler, and knock a nail at each end of the line.

2. Secondly, lean the round tube against the nail, fix it with a marker pen, and slowly turn the round tube until a complete circle is drawn.

3. Then install the cutting piece and cut the circular tube according to the circle. Cut it slowly. If it's crooked, trim it along the lines.

4. Finally, measure the radius of the circular tube, find the center point of the circular tube and mark it, mark both ends of the circular tube according to the incision, draw a line with scissors, and trace the line with a marker.