What is the purpose of a "gavel" in a courtroom?

The gavel serves a crucial role in the courtroom by signaling for order and establishing authority. When the judge strikes the gavel, it serves as a clear indication that court is in session, and it helps to command the attention of all present. This action is essential for maintaining decorum and managing the proceedings effectively. The use of a gavel is a traditional practice that emphasizes the seriousness of the court's business and reinforces the judge’s role in overseeing the proceedings.

Other options do not accurately reflect the purpose of a gavel. For instance, the gavel is not designed to unlock doors or hold documents, nor is it intended to be used as a weapon, which would be contrary to its primary function of maintaining order in a judicial setting. Thus, the correct answer captures the essence of its function as a tool for establishing control in the courtroom environment.