We have a free standing fireplace and we need to replace the support box. It has rusted and in one section there is a hole in the box. Have not had any luck so far with the few fireplace repair companies that are in our area. Have been trying to find a support box online and have found some but don't know how to figure out what size box we would need. The one we have now is a square box aboujt 18x18. If anyone could lead us in the direction to try to fix this would be greatly appreciated The support box we have now is also a flush box the bottom of the box.Thank You!