A more thorough explanation:

Low-grade security refers to a type of security that is not very strong or effective in protecting something or someone from danger or harm. In the context of finance, security refers to collateral or assurance given to guarantee the repayment of a debt or the fulfillment of an obligation.

For example, if you borrow money from a bank to buy a car, the car may serve as collateral or security for the loan. If you fail to repay the loan, the bank can repossess the car to recover its money. However, if the car is old, damaged, or has a low resale value, it may be considered a low-grade security because it may not be enough to cover the full amount of the loan.

Another example of low-grade security is a stock or bond issued by a company that is not financially stable or profitable. If the company goes bankrupt or defaults on its debt, the value of the stock or bond may decrease or become worthless, leaving the investor with little or no return on their investment.

In summary, low-grade security refers to a weak or inadequate form of protection or collateral that may not provide sufficient assurance or guarantee of repayment or fulfillment of an obligation.