Many fireplaces have openings ash dumps and clean out doors to make it easy to clean up the ashes in the fireplace. Here are a couple options we normally have on hand. If these dont work, we can also do custom

These ash dumps come in 3 sizes

4" x 8" (with a 6" x 10" flange)

7" x 10" (with a 9" x 12" flange)

5.5" x 7.5" (with a 7" x 9" flange)

These clean out doors come in 2 sizes

8" x 8" (with a flange of 10" x 10")

8" x 10" (with a flange of 10" x 12")