A square is a ruler that is pressed on the mark. Use this square-shaped to press accurately and cleanly. In addition, when using the technique of overlapping pressure, you will need a rectangle. There are also a variety of materials, such as acrylic, bamboo, and wood, this product is made of acrylic. The advantage of acrylic is that it is stable and resistant to temperature and humidity. It is also transparent, so you can see the paper through, so you can check where you press it.