This time I was brought in to make some concrete block "walls" for a basement moisture sealer commercial. Not only did the owner of the basement they were shooting in not agree to them painting their nice white walls, the storyboard called for unpainted walls, and the producer was bright enough to realize that they probably wouldn't get it on their first take.  Solution? Make some replaceable wall panels.  They figured 4 should do it, so that is what I built.  Often, one gets creative to achieve the illusion of a finished prop; in this case, I felt the best way to mimic concrete blocks was to simply sculpt them out of concrete.  They were just thick enough not to crack, and still light enough to carry around (and hang!).