The TDI works with an open loop into which you distribute the dubbing or fibers. Close the loop before rotating the tool so that the materials remain trapped between the two strands. Measure out the material according to the length of the shank or collar you’re tying: using too much will result in a strand that’s too thick for small hooks. Light brushing releases any fibers trapped in the twist. The strand is then wound in turns spaced closer or farther apart depending on the desired density.