So, when society collapses, and some folks have a few small bars of gold stashed away in their basements, how will bartering with that bar of gold be accomplished?

I can imagine a gold coin will have some small nominal value, say $100-$200, but a solid bar of gold will be very hard to break apart. What's a poor boy to do? I certainly don't think it's a wise idea to trade a small bar of gold for a loaf of homemade bread. How will that transaction be completed?

Yea, I know some redneck gold hoarders will step in and roll their eyes at my question because they've already broken their bars down into something, but please tell me what that something is.

Thanks.