The majority of structural fires occur in one- and two-family dwellings. Often, these fires occur in structures that contain occupiable half-stories constructed with knee walls. Building construction containing knee walls can be found in every community from urban to rural, in older legacy homes, as well as in modern pre-manufactured truss homes. Fires involving the knee wall void spaces present incredible challenges to responding firefighters and have resulted in numerous mayday transmissions. Knee walls can conceal tremendous amounts of fire or combustible gases that are waiting for the proper mixture to ignite. As soon as members open up the knee walls, extreme fire conditions can erupt with little to no warning. Attendees will learn the severe hazards that knee walls present, how to recognize them early in the operation, and how to apply modern fire tactics to safely mitigate incidents involving them.