Abstract: The present invention relates to a resilient, non-rubberoid composition which can be cut to form an impenetrable barrier along a corrugated metal sheet joint to prevent egress of hot, noxious, gases from the interior of the building formed by such sheets. The joint closure material is permanently flexible and therefore resists cracking from vibration experienced in such environments. The method of inserting this material and sealing the joints consists of shaping the material, applying an elastomeric material to the surface of the seam to which a seal is to be made, applying the joint material and joining the two sheets with screws which penetrate both the sheets as well as the filler material. The use of elastomeric heat resistant material seals the entirety of the seam and prevents egress of the gases through the joint.