I just finished weaving a short Japanese kimono jacket (called a haori) for a friend. I added braids on either side for a closure and created these braids using a circular piece of cardboard with a hole in the middle (like a donut.) I've tried to explain the process of working with 8 pieces of yarn to "weave" or braid the cord on my projects page. Here are some photos: PRETTY SIMPLE TOOL! If there is enough interest I can do more step-by-step photos, but the YouTube video that I've mentioned in my Project Page does a great job of explaining the technique.
detail of the kumihimo braid on the haori
the loom with marks for notches ...