My V-cut was never able to cut something like a seatbelt, and deffinetly not now because it's dull. However, I do find it useful for fishing line and other light duty operations, and it doesn't take up any space internaly as I mounted it on the outside of the tool (the bolts are long enough). it doesn't need to lock because the force applied is pulling parallel to the v-cut. All in all, it is a good idea of a tool, but not exactly ready for anything thrown at it. I think it needs to be bigger and sharper, then it would cut belts, and be extremely handy mounted on the outside if the tool.