How size and select heddle rods
I always suggest buying rods in person rather than online. For ease of use and better sheds you will want the straightest rods you can find. To test how straight the rods are, simply roll them on the ground. If the rod does not roll, don’t buy it. You, ideally, want a rod that rolls easy and quietly.
You may use any diameter and material rod that you wish, but I highly suggest getting 7/16” diameter dowels (about 11mm) out of a hard wood. Keep in mind that the Tabby Jack block is 2.5cm wide so you want the diameter you choose to allow for two dowels to sit on the block, so anything bigger than 7/16” or 12mm may be too large. You also want a dowel that is not going to bow or snap under pressure while using. A metal rod is also an option.
To get the correct length of dowel rod, measure your loom’s frame, behind the heddle rest. In the picture below you can see that the frame of my 12” Ashford Knitters loom is 40cm (about 15.5 inches). Take that measurement and add 4cm (1.5 inches). This number will be how long you want your dowels. In my example, I want dowels to be at least 44cm long (17.5 inches). Feel free to add more length as you see fit. The numbers above are the minimum you will need.
Below is a video of how to pick out the best rods. After you pick out the number you need, cut them to the length determined above.