I think you are referring to the card guide. Yes they are easy to replace. You just loosen two screws and it pops out. If it has vertical hash marks, and you want them to line up, then you will want to get the same size scale (pica or elite). The Smith-Corona card guides are pretty compatible between models. If you don't want the plastic, the metal card, seen in many Galaxies, as well as other models, would likely work, as well. One of my pre-war Sterlings had a Galaxy (or similar) plastic card guide in it when I bought it, so older card guides would probably fit, too.