WASHINGTON — Twenty-one years ago, Capitol Hill carpenters custom-designed and built a pair of curved tables that could fit in the cramped Senate chamber and serve as work space for the House managers and White House lawyers during the impeachment trial of President Bill Clinton.

Now, after sitting in storage for more than two decades, preserved as historical artifacts that might never be used again, the tables have been dusted off and moved to the Senate floor, part of a physical transformation inside the majestic chamber as it is converted from a place where legislation is debated to a one-of-a-kind courtroom where the fate of a president is decided.

“They made them after the impeachment articles were voted on,” James W. Ziglar, the former Senate sergeant-at-arms, said of the tables. Mr. Ziglar was in charge of the logistics for the Clinton impeachment trial in 1999.

On Friday, the large tables were again wedged between the front row of the senators’ desks and the marble-and-polished-wood Senate rostrum, so they could be ready next week for the start of oral arguments in President Trump’s impeachment trial.