French knitting is also called "spool knitting" or corking. The "spool" is basically a tube with four tines at one end. The yarn is looped over each individual tine resulting in what is basically a knitted rope. These ropes are often sewn together in a spiral shape, flat for a rug or in a curve cone shape for a hat. Many people used to make their own spools by taking an empty spool of thread(a wooden one of course) and hammer four nails into one end. Knitting frames are often a similar idea, especially the round ones.