Ruth, I wondered that too when I read this, if it is not on correctly it will not work, that arm on the side has to be over the screw. Also is it a free motion foot or a walking foot as they are very different. If it's a walking properly putting it on and feed dogs up. If free motion foot dogs down, properly putting it on and the stitch length is up to you or I should say your hands and how fast you are sewing.