A commodity future is a promise to buy or sell a fixed quantity of a physical good at a set price on a set date. The NYMEX WTI crude oil contract (ticker CL) is a promise covering 1,000 barrels, and its small print is brutally specific: whoever still holds a *long* position at expiry must take physical delivery of the oil at the tank farm in Cushing, Oklahoma. This single clause is what turned a price into a trap.