When beefing up the security of our house a few years ago after an attempted, unsuccessful burglary I was struck by the thought " If I loose my house keys when I am out, how do I get in"? Previously I knew a few weak spots that would allow entry without too much damage. These are now rectified.
The answer is fairly simple however, leave a set with a trusted neighbour, relative etc. This of course may not be so easy on a narrowboat. No I don't recommend a secret key beneath a flower pot or anywhere else for that matter.
My aim has always been to deter the opportunist, I know I will never stop a professional burglar.
It is worth considering, If I lost my keys how would I get in?