You're in luck! I'm an insurance agent. They are covered from fire, theft, vandalism, tornado, etc, just like the rest of your personal property. However, that is subject to your deductible.
You can also schedule the the knife or knives in question, like jewelry, computers, fur coats, etc. By doing so, you avoid paying your deductible. However, it is an "agreed" value, and you would need proof of purchase or an official document stating the value as such. That gets tricky if you buy/sell/trade in the exchange.
Also, there is no real way to insure customization, so if they are stolen, burned in a fire, taken in a natural disaster, etc, you would get the value of the knife itself.
It was like with my Camaro I had, the vast amounts or modifications would not be taken into effect in a total loss.