Delivery Instrument
  
Receipts are always important to prove ownership, and provenance is the key to final transactions. Whether it's lingerie purchased at Victoria’s Secret, a new Porsche from the auto dealer, or the Whopper with fries at Burger King, receipts are critical for establishing ownership rights, so that you can choose to give the lingerie to a significant other, register the Porsche with the DMV, or give the Whopper and fries to your kid. Without the receipt, someone could contest your rights.
While the majority of people trading the commodity futures market are speculators, there exist actual commodities, either in storage somewhere or en route to a delivery port that underlie those contracts.
A delivery instrument is a shipping receipt, warehouse receipt, or comparable document that is given to the futures contract holder, who has the choice to take delivery and exercise the contract...or sell the contract and transfer ownership accordingly.