Without looking for the issue of Handwoven, I assume that the three threads in a dent are not on the same shaft (harness). Only those threads on the shafts that are tied to a treadle will rise (or lower) when the treadle is depressed. If the threads in the first dent are threaded on shafts 1, 2, and 3, and shafts 1 and 3 are tied to treadle 1, then threads 1 and 3 will rise (or lower depending on your loom) when treadle 1 is depressed. The thread on shaft 2 will stay put. Hope that this helps.
You can either buy a raddle or make one. It is one of the simplest pieces of weaving equipment. When I learned how to weave, my instructor strongly recommended that each student make a raddle--a length of 1" x 2" board and finishing nails. The rubber bands that keep the warp from jumping out of the sections have been replaced many times, but 35 years later, I'm still using the raddle.
I have woven with both brushed and loop (boucle) mohair using both for warp and weft. The yarns are approximately 900 yds/lb and sett at 6 epi in a 6-dent reed. A 2/2 twill at 6 ppi makes a scarf with a nice drape. The fabric will look very open and gauzy. Wash the scarf in room temperature water with mild soap and hang to dry. When dry, hold a steam iron above the fabric and brush with a natural bristle hair brush--soft and fluffy!
I'm pleased that I painted not onlythe area around the eyes of my Texsolv heddles, but also the cut ends at the top. When I need to check which shafts are raised when I'm weaving, it is quick and easy to take a look at which colored ends are sticking up.
Also, if your heddles are not already colored, leave white as one of the colors used--saves on paint and labor.
You can also paint every 10th (or whatever counting system you use) a different color. Although it is a chore to do, it makes counting heddles much easier in the future.