While starting the process of finishing the basement, I pulled down some of the old cheap styrofoam they had stuck on the interior of the block wall only to find a 6"+ size hole where an apparent woodstove pipe used to exit the basement. The hole is not noticable on the outside because of a floor bed they had built up over the years. The blocks are all hollow, so I'm wondering what the best way is to go about filling the hole. I'm hoping there's a solution other than knocking out all the "holed" blocks and replacing them. Any thoughts would be appreciated!