2. Balloons of two colors. (Don't use hydrogen when blowing balloons; hydrogen is dangerous and flammable; Using helium).
3. The pillars on both sides of the arch are hollow steel pipes.
4. Cross two groups of balloons on the steel pipe, such as X shape, and add them one by one. Pay attention to the direction of rotation of the colored balloon.
5. Two steel pipes are finished. Clip the balloon to the length you need with wire just now. Then insert the iron wires at both ends of the balloon into the hollow steel pipe column just finished.