It's merely some 1 x 2 boards with some drilled holes and nails. The nails across the top are 1/2" apart. These boards (called rails) are 2 feet each.
The holes in the side rails are so the size can be adjusted up and down. The bolts are long enough to go through two pieces of wood. The bolts have wing nuts on them. To make a shorter rug, I simply move the top rail down to lower holes.
The legs are simple design. Just enough to hold the frame while I work. I drilled holes through the sides of the boards to hold the bolts for the legs. The reason I didn't make the legs permanent is so I can change the rails for different size rugs.
I have rails in different lengths and widths. To be sure the holes lined up perfectly I taped two rails together before drilling the holes. This makes the rug frame adjustable in many different sizes. All the top and bottom rails have nails. All the side rails have holes about 2 or 3 inches apart. I painted everything just to make it pretty.
For stringing the frame I use polyester twine. I prefer to us this twine because it drys quickly when the rugs are washed. Jute or fabric twine won't dry as easily.
I make t-shirt memory quilts quite often. I don't like throwing away perfectly good fabrics. The left over backs and sleeves make really good rugs. But... if you have a bunch of left over quilting fabrics they make good rugs too.
I use headless nails to make the rug come off the frame easily. At the end of the weaving process it becomes extremely tight. So tight that in fact I have to use a crochet needle to pull the fabrics through the strings. If you use nails with heads on them it will be impossible to remove the finished rug.
I hope you can follow these directions. Pictures are usually better than words.