I too have someone listed as a "molder" on a census in Pittsburgh, PA. I wasn't sure what type of form maker he was until, I found him also listed on another census as an "iron molder." With the iron and steel business in Pittsburgh, PA, that made sense. However, when this person then move to an agricultural area of Kansas, and still was listed as a molder, I suspect in that area he worked for one of the railroads making parts. This person also worked for a furniture manufacturer so he may have made "metal beds??" I still have not come to any firm conclusion. But, one way to seek information would be through City Directories. Many times the occupation is given and the actual employer is also listed for the person. Hope that helps !