An elegant, budget-friendly solution for all your crochet granny square blocking needs.   As someone who decides to do all their blocking at the end, instead of as I go… 

This model uses 1/4" wooden dowels (can be purchased at any craft or hardware store), offering far greater strength and durability than 3D-printed rods. Reinforced layers through the center add extra stability, and the compact design facilitates easy storage.

Preferred settings:

• Print settings: 0.20mm Quality or Speed
• Infill: 15% 
• Fill pattern: Gyroid (preferred)

Print will automatically generate extra “infill” layers down the center, so there's no need to increase infill for strength. 

Additional items:

• ¼" wooden dowels - available at most craft or hardware stores. I find 6"  long to be a good size

Comments

• “Blocking Corners” are available to keep squares “straight”
• Dowels will bend if you are trying to stretch out the squares, I would suggest just printing 8 copies and placing them at both ends. If you're using longer dowels, you may need to print out an additonal set down the middle to keep the dowels from bending inwards.
• The circles will print out as hexgon, thats on purpose to allow for dowel tolerences. There is a "Tester piece for tolerances if required. The dowel will fit snugly.