Living in McCall Idaho has its perks, but one of them in NOT getting snow off of the roof. Lots of other folks have built these tools, so my design is standing on the shoulders of other DIY-ers gone before me.

The basic idea is to make a giant cheese slicer. The slicer cuts the bottom from under the snow and lets it slip-and-slide off the roof. The primary issue solved is "ice damming". If you have a warm roof the melt can come down under the snow to the end of the roof and freeze. Then it backs up under the shingles and leaks.