A more thorough explanation:

Definition: Certus plegius is a Latin term that means "sure pledge." It is also known as salvus plegius, which means "safe pledge." In legal terms, it refers to a satisfactory pledge.

Example: If someone borrows money from a lender, they may be required to provide a certus plegius as collateral. This could be in the form of property, a valuable item, or a guarantor who promises to pay back the loan if the borrower cannot.

The certus plegius provides assurance to the lender that they will be able to recover their money if the borrower defaults on the loan. It is a way to reduce the risk of lending money and protect the lender's interests.