The double zipper is a fertility symbol relating to the ancient pagan mating ritual that Northern European Carpenters were key participants in.
After traditionaly constructing a post and beam male and female effigy the carpenters would strip naked, light the effigy a fire, drink copious quantities of Ale and proceed to......
Well, I think you get the picture.
For further reading on the subject see;
Alfred Winslow's "Mating Ritual's And The European Carpenter AD 806-1278" Sub-titled" Double Zippers And Their True Meaning.
-Collin
