If your concern is more with being tampered with than stolen or destroyed in a fire, you could get away with a sturdy locked trunk. It wont keep out someone who really wants to get in. But will keep out the honest. For an added layer of protection gun locks are a simple and inexpensive solution. You could even leave the guns exposed but with locks and stick the knives in an inexpensive fire safe. No one will get hurt and it as easy as pie when moving time rolls around.