Phyllis,
You need a rotary cutter that is sold in quilting or crafting stores such as JoAnn's, Walmarts, or your local quilting stores. What is recommended from Harbor Freight are just the circular blades that fit into the rotary cutters. Here are some videos that give you some idea of what they are, and how to use them.
http://www.google.com/search?hl=&q=r...e=univ&tbs=vid:1&tbo=u&ei=hDyvTNvNOIGKlwfIvt2NBQ&sa=X&oi=video_result_group&ct=title&resnum=7&ved=0CF4QqwQwBg&fp=9f2370386c77b788
Word of warning .... please be careful with them. They are sharp as razor blades. :-)