The key is to connect rectangles-triangles-rectangles-triangles of the same color and change the direction. It will be easy to make a ball by mastering this law.

　　To make a ball with a magic ruler:

　　1. Fix the first paragraph, and turn the second paragraph counterclockwise once, and a (blue) rectangle and triangle will appear.

　　2. Rotate the third paragraph counterclockwise once, a triangle appears, the fourth paragraph rotates clockwise once, and the fifth, sixth and seventh paragraphs rotate repeatedly. At this time, a corner of the ball has been revealed.

　　3. Repeat the same rotation. The eighth section rotates counterclockwise and the ninth section rotates clockwise, which is folded into the following figure.

　　4. Continue to rotate counterclockwise and clockwise repeatedly. In the process of operation, it is necessary to check at any time whether all white triangles are connected with blue rectangles.

　　5. The last two paragraphs also repeat clockwise rotation and counterclockwise rotation.

　　6. Finally, turn the 22nd paragraph clockwise again to finish.

　　Precautions:

　　1. The above method is only applicable to the 24-segment magic ruler. Check at any time whether all the magic rulers are connected by white triangles and blue rectangles.

　　2. Playing with children can cultivate children's interest in entertainment, develop intelligence and exercise patience.