I've heard it all before,
Sell doorknobs at my door

AND ALSO

Sell doughnuts at my door

The story:

I always thought it was doorknobs like it was supposed to be some
ironic or useless sales pitch in which life is pointless, etc. you know
how rock can be.... anyway I sang this in the car and my friend said
WHAT? and gave me a weird look. I argued that I was correct and
made a good case until I was proven wrong by the internet....