GAP WaterGuard Rain & Ice Protection is a specially designed and manufactured, self-adhering, SBS polymer modified asphalt underlayment for use on steep slopes to prevent moisture intrusion from ice and wind driven rain, as required by many building codes. GAP WaterGuard Rain & Ice Protection serves a dual role as a flashing membrane, helping protect areas susceptible to leaks such as valleys, roof to wall transitions, and around vents and skylights.