Senate Sergeant-at-Arms Terrance W. Gainer, right, escorting President Obama during a visit to the U.S. Capitol in 2013. (AP/J. Scott Applewhite) Senate Sergeant-at-Arms Terrance W. Gainer, right, escorting President Obama during a visit to the U.S. Capitol in 2013. (AP/J. Scott Applewhite)

In a fleeting moment of unity, Senate leaders put aside their differences Thursday morning to pay tribute to two retiring congressional employees largely unknown beyond the walls of the U.S. Capitol, but well-known faces to senators, staffers and reporters who visit the building each day.

Senate Sergeant-at-Arms Terrance W. Gainer, the chief law enforcement officer for the Senate is retiring this week after seven years in the position. He is perhaps most familiar to Americans on one night every January, when he is seen over the shoulder of the president, escorting him from the Senate side of the Capitol to the House Chamber for the State of the Union address.

Daryl Chappelle is a much-less familiar -- but also critical -- employee. In the past 28 years, he's driven one of the iconic underground subways that connects the Capitol to the Russell Senate Office Building between the two buildings at least 130,000 times, according to estimates by Senate officials. It's likely that most senators, staffers, lobbyists, tourists or reporters who've traveled the route in the years since have taken a ride with Chappelle.

Senate Majority Leader Harry M. Reid (D-Nev.) and Senate Minority Leader Mitch McConnell (R-Ky.) paid tribute to Gainer and Chappelle Thursday morning as both watched from the Senate floor.

Reid said Gainer has done "an admirable job. We're confident of him every day. Under his leadership, the day-to-day operation of the United States Senate has never been better."

McConnell noted that he often disagrees with Reid's decisions, but that "picking Terry was one decision that he got just right."

Gainer began his career as a Chicago police officer -- and his first assignment was to provide security at the 1968 Democratic National Convention. He rose through the ranks and eventually came to Washington, where he served as deputy chief on the Metropolitan Police Department. He moved to Capitol Hill next, where he served as chief of the U.S. Capitol Police, and, in 2007, became Senate Sergeant-at-Arms, the lead law enforcement official in the upper chamber.

Chappelle came to work for the Senate Superintendent's Office at the age of 19, shortly after graduating from Spingarn High School in the District. After working in the labor division for several years, he became a mechanic and began operating the Senate subways.

"He has a smile that is just -- that just covers his whole face," Reid said of Chappelle. "He has a voice that's infectious."

McConnell agreed, adding: "Daryl is the undisputed champion of making the most of a brief encounter." He recounted how one of his staffers had recalled her first day on the job in the Senate as an intern:

"She had just moved here from Kentucky for an internship. She didn't really know her way around, and she was pretty nervous. It must have showed, too, because after giving her direction to the office, Daryl not only gave her a big warm smile, he also left her with a message that she has never forgotten. As she stepped off the train and headed  off to her first day on the job, Daryl looked at her, and he said, 'Everything's going to be okay. Everything's going to be okay.'"

"He showed us all the power of the small gesture," McConnell added. "He reminded us that when all is said and done, what really matters is how we deal with each other."

Several other senators later added their own tributes Thursday morning. And others stopped by Chappelle's subway this week to thank him personally: