ATmega168 Lock Bits???

And it is NOT possible, to "reset" the lock bits.
That means if i need to burn a new sketch, i have to throw away the 168 and take a new one...

I was under the impression that if you did a full chip erase then the lock bits were reset (but obviously the whole chip is erased)?

I had a very quick look online for something that said this, but didn't find anything.

--Phil.