My guess is that the longer straight looms are for blankets.

I make a shawl by wrapping around from the first point (where the nobby is) all the way around.. and instead of joining and continuing like you would to make a whole circle, I wrap back around the last post and come all the way back to the start.
Because its a funky number I usually wind up with a wrap 3 posts, skip 1 post, wrap 2, skip 1, wrap 3...etc.. all the way around, this gives me a wrap 3 on one end and a wrap 2 on the other. Kind of like a top and bottom.
I just keep adding and working back and forth rather than in a full circle until it is the length I want.
It comes out about 14 inches wide when done.
Then I finish end edges with fringe.
It is like an ultra wide scarf.

To make a shrug, start with making a circle, then work the circle until you are 6 or more inches past your finger tips (this would be from the armpit.
Once you reach the desired length of your sleeve, change your working from a complete circle to back and forth, like you would for the above shawl.
Work across the width of your back and then close your sleeve again and work in a circle to make the other arm continuting past your finger tips.

The disadvantage to making a shrug this way, is there is no real way to gusset or raglan the sleeves to the body. Thats why I work it past my fingers a good 6 inches. So I can get enough slack to get it around the crest of the shoulder.

I am going to have to make another one, and even another shawl.. I keep giving them away without photos. (I don't think about pics of projects... Bad habit)