The two corners of colored paper are folded in half to form a triangle. 2. Find the midpoint, fold the right corner to the left, then turn to the back and fold the right corner to the left, and the edge lines should be aligned. 3. Draw the pattern of window grilles on the paper with a pencil, and then cut along the pattern with scissors.

Because the cutting method of window grilles is random and the folding method is different, the cut window grilles are also different. Generally, there will be quadrilateral symmetry, octagonal symmetry, dodecagonal symmetry and so on.