Snow Guards.

Snow guards are a must-have for any roof that gets a lot of snow. Snow guards come in many different shapes, sizes, and styles, but they all have the same goal: to prevent snow or ice from falling off of your roof and onto your landscaping, cars, or people below. They hold the snow on your roof so that it can slowly melt off from the warm sun or other heat sources. 
Snow guards are an important part of any gutter system because they help keep people safe and prevent damage to your property during snowstorms. Snow guards also reduce ice damming on your roof by allowing water to drain off instead of collecting, where it could freeze over time, re-melt and then leak into your home through the attic, ceilings or walls.
Generally, snow guards are used on homes or businesses with very steep roofs or roofs made of slate, metal or wood. Asphalt roofs usually have enough grip to prevent snow from sliding off your roof. As the snow accumulates on your roof and melts in the sun, it will bond together. The bonded snow will then freeze and create a dangerous block of ice. Even if your attic is properly insulated, warm rising air from your home will cause the snow to melt, and the entire roof's surface will become slick and cause the ice to slide off the roof and cause damage to your property or harm people. Snow guards are designed to hold the snow on your roof and prevent these issues.