Snow guards are devises that are attached to the roof structure in order to provide form retention and control the snow from avalanching in large sheets. The snow guards need to be applied in sufficient quantity according to a prescribed pattern in order to be effective. Snow guards are intended to reduce snow movement and provide for a controlled melt and breakdown of the snow mass into smaller sections. Snow guard placement will vary from region to region and will be influenced by roof pitch, the lengths of roof runs and roof features (dormers, valleys, chimneys, etc). A qualified professional should determine placement. Snow guards should never be placed beyond the bearing wall on an extended roof section (cantelever). This can result in ice damming and cause structural damage.