See instructions: Varpapuu Loom
When I added the other 4 shafts to make it 8 shaft functional, well I had problems. The shed was not opening with my tie up. So back to the internet, search and I found some more information about these older looms. I wanted to post this info.
Of course not all countermarch looms are equal. I have been taking lessons with Jane Stafford and her studio has the Louet "Spring" looms. These are a parallel countermarch loom. As well, this loom has a floating front beam, so the warp will always be a uniform tension, which is helpful for even weaving. I think the Spring is a really well designed loom, it is unlikely any owners would part with this loom, so you won't see used "Springs" for sale very often.