Try going to the Olfa website that is listed on their packaging. I think it is really just Olfa.com. They have videos showing how to replace the blades in their different cutters. Now I thought I didn't need to do that because I have been replacing these blade for about 5 years, but all of a sudden my blades were going bad really fast. So out of frustration, I decided to look at their video and wouldn't you know, I was not doing it correctly. It was a very simple fix after I watched that. I think because the blades actually last so long, I forgot how to replace them, even though I thought I was following the diagram on the package. Something about seeing it done just clicked for me. Good luck.