The parties to a case are added when the case is issued – either manually by an agent, set in a template or by an integration. By default these person's party details (such as name, e-mail, etc.) are set when the case is issued. Only the person specified can sign the case.
However, with open parties the person invited to sign can change their own party details before signing. This is useful when you want to sent out a case to someone, but you want to allow the person to forward the case to someone else for signing.
It's also used when with Web automation, where you publish a form or an agreement on your website that you want anyone to be able to sign.
To make a party an Open party, go to the menu for that party in the Web office.
As opposed to normal parties, open parties are not obligated to fill in their e-mail address. If they want to get notifications regarding the case they need to enter their email address.