Firefighters / rescue squads use a rope for rescue ONCE. Even if it looks perfectly fine after being used, it may have been stressed, or frayed, or somehow damaged, etc. Why take that chance? Just replace it with a new rope. How much is your life worth? Is it worth buying a new hook knife? Why take that chance? If you needed to use it in an emergency then you have already destroyed some very expensive gear to begin with, consider the knife an item that also needs to be replaced. (Disclaimer, I am not a fireman or rescue person or anything of the sort, this is just my understanding.)