A more thorough explanation:

Definition: A vas is a pledge, surety, or bail. It is often used as security for a criminal defendant's appearance in court. In Roman law, a vas was a special surety for the defendant if there was an adjournment in jure.

Example: If someone is arrested and released on bail, they may have to provide a vas as a guarantee that they will appear in court for their trial. The vas could be a sum of money or property that is held by the court until the defendant's case is resolved.

The example illustrates how a vas is used as a form of security to ensure that a defendant appears in court. It is a way to guarantee that the defendant will not flee or avoid their trial.