Tools/materials: scissors, ruler, pen, origami.

1. In Zhang Kuan, a rectangular origami with a length of 10 cm is vertically folded in half, and then folded in half, thus forming four layers, counting from the upper right corner 10 cm.

2. Measure from the upper left corner to the left, 10 cm, and then point down.

Connect these three points with a ruler and two diagonals.

4. Measure 5cm down from the center of the short diagonal and connect them with dotted lines.

5. Cut off the long diagonal and dotted lines.

6. After cutting, spread it left and right, so you can use sewing machine and film loading, or you can use elastic band.