A more thorough explanation:

A supplemental surety is a person who is primarily responsible for paying off someone else's debt or fulfilling their obligations. This person is similar to an insurer, but they often do not receive any compensation for taking on this responsibility.

It is important to note that a surety is different from a guarantor. A guarantor is only liable to the creditor if the debtor does not fulfill their duties, while a surety is directly liable.

For example, let's say that John wants to rent an apartment, but he has bad credit. The landlord may require a supplemental surety to co-sign the lease, meaning that the surety is responsible for paying the rent if John cannot. In this case, the surety is directly liable for the rent payments, even though they are not living in the apartment.

Another example could be a construction project. The contractor may require a supplemental surety to guarantee that the project will be completed on time and within budget. If the contractor fails to fulfill their obligations, the surety is responsible for completing the project or paying for any damages.