Hey everyone. I hope someone can point me in the right direction. I decided to clean my insert today in preperation for the upcoming season. I brushed the liner, cleaned the cap, and vacuumed out the insert. I then took the outer moulding off of to inspect the fireplace firebox and found some mortar loose on the left and right side of the outer firebox. The mortar connects the firebox brick to the outer hearth bricks. What can I use to fill these two gaps? They are exactly 1 inch wide. I included a picture in case my description doesn't make any sense. Sitting in the firebox is a regency wood insert and it has an insulated stainless steel liner. Thanks in advance. Mike.