How do you cut your formers?

Here is what I do... fixed blade utility knife two or three passes.... I have kept trying different utility knives that have those little snap off blades but they never stay retracted when I pull even with the little lock thing on.... they also seem pretty floppy compared to the fixed blades. What do you guys use? If you have one of those snap off jobbies you are happy with can you tell me what kind it is and possibly post a pic?
Thanks!
Chris