Have you ever looked at a larger old Navajo rug and wondered, what are those white dots going across the weaving from side to side? Some may think it is a damaged area or weaver mistake and remove them.
These are weavers sew lines. As far as i know along with "Lazy Lines" (to be discussed at a later time) were very important. Say a weaver lived in a hogan and was able to fit maybe an eight foot wide loom into her hogan but was not able to fit one that was maybe ten foot high. This technique would have been necessary to accomplish weaving a 5'x7" weaving. Most certainly you would have used this technique in the winter months to weave indoors out of the elements. In the summer months a tall tree branch could have doubled as the top support of the loom.
This technique also keeps the weaving at shoulder level or below. As you weave you can stack blankets on chairs to lift yourself up off the floor to make yourself higher then your weaving area. Eventually run out of safe options that are comfortable.
Try to imagine, taking all your dishes out of the drawers and washing them above your head at an outward angle until all were cleaned. It would eventually cause you agony and this in turn would make you want to quite trying. So, this was an ergonomics technique in most cases.
Here are pictures of my trusty rug, I am weaving on a Navajo loom. These pictures show how the finished weaving is dropped about 8 inches to keep the unfinished area at or below shoulder height. Enjoy!