hammer charge
n.— «Burrell had the jurors brought into the courtroom and directed them to renew their efforts to reach a verdict.…The instruction Burrell gave the jurors is sometimes called the “hammer charge,” and the law allows it to be given only once.» —“Hayat jurors told to keep deliberating” by Denny Walsh, Dorothy Korber Sacramento Bee (California) Apr. 25, 2006. (source: Double-Tongued Dictionary)