I think the most important part of Daves post was the fact that it was a commercial building, the edges of the glass are usually deeper on commercial glass and that makes using a wagtail or any other squeegee on a pole easier, the same can not be said for residential , though, the squeegee has a tendancy to slip off the edges on house windows and while with a bit of practice you can stop this happening , you need to be more careful and this slows you down