I must admit I do a pretty nice lapped zipper but one particular point always gets my goat.  Exactly where do you start sewing the un-lapped (hope there is such a word) side of the zipper.  Is it just above the zipper stop, behind it?  I've tried it in different positions, and of course  had different outcomes.  What is the rule?  I'm teaching my grandaughter to sew and before we tackle that pesky zipper I want to make sure I'm giving sound advice.  HELP!!!!