The connecting straight top is needed when ordering the Sylvia cabinet models 1350, 1810, and 1810Q and you prefer the cabinets in a straight configuration. The straight top connects to the cabinet on each side and sits on the sewing chest model 350. The straight top secures to each cabinet with cam locks. If you would like the cabinet completely level when the machine is all the way down and the cabinet completely closed then order two 395′s.