also "cash on the barrelhead". Means that you give me cash, and I'll give you the product at that time. No credit no delivery.
Buddy: You ever think about selling that old juicer?
Barbara: I'll give it to you for $20 - cash on the barrel.
Buddy: OK, here is the money.
Barbara: Thank you, here is the juicer.
Buddy: It has been a pleasure doing business with you.
Barbara: The feeling is mutual.