This is a basic blocking tool for crocheting Granny Squares to keep them all the same size and with straight edges.

I designed this tool in OpenSCAD so that anyone can download the program OpenSCAD and adjust the parameters in the file. The major parameters to change are: 

• dowel_size controlling the diameter of the cylindrical dowels needed for blocking all four or more corners of the Granny Squares / Hexagons. Both files are sized for approximately 4.8mm to 5mm diameter dowels at a tight fit. Customizing the file will accept up to diameter 14mm.  The holes will always be 1.5cm apart unless you choose to alter this parameter too but doing so can produce a wonky design.
• block_tool_length which is the the physical size of this square tool.  150mm is provided and tested and I think 195 or 210 would be good to size up too. To me, 150mm seems like the smallest I would go to have options for many sizes.

I used a 0.6mm Nozzle and 0.4mm Layer Heights. Your tolerances may vary.

I will be using knitting needles (pictured) instead of buying or printing dowels for this tool.