It is quite difficult to weave bands, i.e. things like guitar straps or bag handles on a Rigid Heddle loom. The pattern is warp-based so the weft is hidden by the warp. High tension needs to be applied and picking out the correct pattern is a struggle.
I have found the answer in a book from the shop Weaving Patterned Bands by Susan Foulkes, and the answer is a Sunna reed. The 5 pattern slots and holes are the same length and this makes them stand out and it is easier to pick up.