I used this to fill the 1/2 inch gap between the steel cornice frame and the stone face. First I filled the gap with folded wire mesh. This product easily adheres to the fabric and provides a strong and reliable seal. It dries out a lot, especially after using the fireplace. Note: I smeared the rest of the product onto the sides of the firebox to hide the gray cement I used earlier. I smeared the black cement very thinly and after the fire I noticed that the cement became crusty and flaked off easily. Not a big deal, and for a major repair I did it perfectly. Very happy with this product.