Gothamist helps out with your WTF:
According to KosherDiapers.com their product's Velcro fasteners have "no חשש, whatsoever - not when opening and not when closing the strips." Thank goodness! See, and this was news to us (bad Jews that some of us are), the gist of the issue is that the adhesive in most diapers use glue, which is "similar in effect to sewing" which is prohibited on Shabbos. Velcro, however, is okay because "diapers with velcro tabs are permitted because velcro achieves its stickiness by hooking, not by gluing."RELATED: You're not officially a New Yorker until you attend a party in a Shabbos-observant apartment building and realize too late that the elevator is going to stop on every floor so that nobody has to push a button. Lesson learned: If you're coming from another party, pee before you leave or that ride to 27F could be very uncomfortable.