A Summons on Third-Party Complaint is a legal document that is issued by a court to a third party who is not a party to the lawsuit but who may have information relevant to the case. The purpose of a Summons on Third-Party Complaint is to compel the third party to appear in court to answer questions or provide testimony. There are two types of Summons on Third-Party Complaint: a) a Summons for Testimony, which orders the third party to appear in court to give testimony, and b) a Summons for Documents, which orders the third party to produce documents or other evidence that is relevant to the case.