The stocking die has the stocking shape and the cuff shape (and the toe and heel shapes). So the line is to show you exactly where the cuff shape (or toe or heel) is layered on top. There is no way I'm paying that much for a die if I have to do manual cutting with scissors as well.
eta: I do not have this die. Where exactly are the dotted lines?
Wash: "A man walks down the street in that hat, people know he's not afraid of anything."
Jayne: "Da*n straight."
-- my recipes