Hi Crackers, sorry to cause you confusion and concern on my reply to Monale on her thread. A ruler base is needed for longarm machine that is mounted on a rack. Most domestic machines already have a surround of some sort going around the free arm. As in the pic Monale posted above. Some people call it an extension. About the only reason you would take the surround off of a domestic is in garment sewing for things like sleeves and cuffs. You most likely have a surround on your machine. I have never heard of a modern sewing machine not having one and quite honestly most vintage machines have them as well.