This ruler is designed to work with blocks on a 3 inch X 3 inch grid which is any block divisible by 3. The most familiar block in this category is the Nine Patch Block. Use this ruler to produce perfect Snowball Blocks in five different sizes. This ruler also works well with the following grids: 6 inch X 6 inch, 12 inch X 12 inch, 24 inch X 24 inch, and 48 inch X 48 inch. In addition, the ruler can be used to “Snowball” corners of rectangles as well. The possibilities to produce spectacular results are endless. There are NEVER any little bitty squares to sew or position in place.