What borrowing instrument allows for additional sums of money to be loaned against the same security device?

The correct answer is open-end mortgage, which is a type of borrowing instrument that allows a borrower to obtain additional funds using the same security device—the property that is already mortgaged. This type of mortgage provides flexibility for the borrower, who can borrow more money later without having to take out a new loan or refinance the existing one. It essentially enables the property to act as collateral for future loans, maintaining the original terms while allowing for additional borrowing as needed.

In contrast, other options do not facilitate this kind of flexibility. A subordination clause pertains to the priority of liens on the property, which does not inherently allow for additional sums to be borrowed. A partial advance refers to a disbursement of a loan in segments, rather than all at once, but it doesn’t imply ongoing access to additional funds. An obligatory advance suggests a commitment by the lender to provide certain sums at predetermined times, which does not include the advantage of borrowing against the same security for future needs.