" I guess you invent a short by entering a contract to sell someone gold 6 months from now for a given price." - i.e. a short futures^H^H^H^H forward contract (

" I guess you invent a short by entering a contract to sell someone gold 6 months from now for a given price." - i.e. a short futures^H^H^H^H forward contract (oops, futures are on exchanges and forwards not, I forgot that being exchange driven is part of what makes it a future vs. forward) You could short it like you short a stock - find someone who owns some gold, and have a contract to borrow the gold now, and give it back to them in 6 months, while paying them a small fee while it's outstanding. That's exactly what happens with shorting.