• Delivery may be made with either the owned or the borrowed shares, so it is less risky than an ordinary short sale. The phrase against the box refers to the owned shares that are in safekeeping; formerly, the “box” was a container used to store stock certificates. — Often shortened to sale against the box.
short sale against the box
A short sale of a security by a seller who owns enough shares of the security to cover the sale but borrows shares anyway because the seller wants to keep ownership a secret or because the owned shares are not easily accessible.