N.H. Cir. Ct. Dist. Div. R. 3.9 (pre-e-filing)

A. Whenever a third party is, or may be, liable to a defendant in any pending action for all or part of the plaintiff's claim against said defendant or if said defendant may have a claim against a third party, depending upon the determination of an issue or issues in said pending action, said defendant may bring an action against said third party and, unless otherwise ordered on motion of any party, such action will be consolidated for trial with the pending action or, if justice requires, on such motion said third party may be made a party to the pending action for the purpose of being bound by the determination of any common issues; provided, however, that, except for good cause shown to prevent injustice and upon such terms as the Court may order, no such action will be consolidated with or said third party joined in said pending action, unless suit is brought against said third party within thirty days following the return day of said pending action.

B. A third party against whom an action is brought in accordance with this rule and a plaintiff against whom a counterclaim has been filed may, under the same circumstances prescribed by this rule, use the same procedure with respect to another person and the same time limitation shall apply, except that as to a plaintiff the thirty days will begin to run on the date the counterclaim is filed.

C. This rule shall not be construed to limit or abridge in any way the existing common law practice of joining parties in pending actions whenever justice and convenience require, or the giving of notice to third parties to come in and defend any pending action or be bound by the outcome thereof.

D. This rule does not apply to a defendant who contends that a third party is solely liable to the plaintiff or by a defendant in a tort action as to a possible joint tortfeasor against whom said defendant has no right to contribution or reimbursement.