Alvin - Plastic Snap-Off Cutter - Heavy Duty - The Alvin Heavy Duty Plastic Snap-Off Cutter is a fully retractable Utility Knife with locking mechanism and uses standard 8 pt. large snap blades. Alvin is one of the primary sources for drafting supplies and drawing equipment in the country. Creative Coldsnow is a pround retailer of Alvin graphic arts, drafting and fine arts products.