37 CFR § 2.128 - Briefs at final hearing.
(1) The brief of the party in the position of plaintiff shall be due not later than sixty days after the date set for the close of rebuttal testimony. The brief of the party in the position of defendant, if filed, shall be due not later than thirty days after the due date of the first brief. A reply brief by the party in the position of plaintiff, if filed, shall be due not later than fifteen days after the due date of the defendant's brief.
(2) When there is a counterclaim, or when proceedings have been consolidated and one party is in the position of plaintiff in one of the involved proceedings and in the position of defendant in another of the involved proceedings, or when there is an interference or a concurrent use registration proceeding involving more than two parties, the Trademark Trial and Appeal Board will set the due dates for the filing of the main brief, and the answering brief, and the rebuttal brief by the parties.
(3) When a party in the position of plaintiff fails to file a main brief, an order may be issued allowing plaintiff until a set time, not less than fifteen days, in which to show cause why the Board should not treat such failure as a concession of the case. If plaintiff fails to file a response to the order, or files a response indicating that plaintiff has lost interest in the case, judgment may be entered against plaintiff. If a plaintiff files a response to the order showing good cause, but does not have any evidence of record and does not move to reopen its testimony period and make a showing of excusable neglect sufficient to support such reopening, judgment may be entered against plaintiff for failure to take testimony or submit any other evidence.
(b) Briefs must be submitted in written form and must meet the requirements prescribed in § 2.126. Each brief shall contain an alphabetical index of cited cases. Without prior leave of the Trademark Trial and Appeal Board, a main brief on the case shall not exceed fifty-five pages in length in its entirety, including the table of contents, index of cases, description of the record, statement of the issues, recitation of the facts, argument, and summary; and a reply brief shall not exceed twenty-five pages in its entirety. Evidentiary objections that may properly be raised in a party's brief on the case may instead be raised in an appendix or by way of a separate statement of objections. The appendix or separate statement is not included within the page limit. Any brief beyond the page limits and any brief with attachments outside the stated requirements may not be considered by the Board.