[QUOTE=kjackson;7402745]Thanks, Rob, it's one of the older ones with the arm that goes over the needle (what exactly does that arm do?)
The arm that goes over the needle bar (actually over the screw that holds the needle clamp in place) causes the foot's moving parts to go up and down in time with the needle, so they act as feed dogs for the top layer of fabric. If the arm isn't placed over the needle clamp screw, then those parts don't work properly.
Rob