Jim Harbaugh dusted off his rulebook and flexed his brain muscles on Thursday night.

The Chargers coach earned his team a free three points when the Broncos punted as time expired, enacting a free kick rule that resulted in Cameron Dicker drilling a 57-yarder as time expired to go into the half.

The three points swung momentum toward Los Angeles, which went on a 24-6 run as it rallied for a 34-27 win.

“I’ve been trying to get one of those every game. Cam Dicker stepped up and made it. It was huge and got the momentum back,” Harbaugh said of the obscure play.

It’s the first time in 48 years that a free kick was executed successfully, likely due, in part, to the circumstances leading up to the play having to be very specific.

A free kick can occur when a team punts as time expires in a half and then commits an interference penalty on a fair catch. The receiving time can opt for a free kick field goal attempt — in which the defense must line up further back, akin to a kick-off — or an untimed snap from scrimmage.

In this case, punt returner Derius Davis was attempting to fair catch a punt around the Chargers’ 42-yard line when he was interfered with by Tremon Smith, resulting in a 15-yard personal foul penalty, enforced at the Broncos’ 43.

Harbaugh opted to kick the 57-yard fair-catch kick field goal attempt, which Dicker nailed, rather than send Justin Herbert out for a Hail Mary.

“It’s cool. I didn’t know that was the case,” Dicker said. “It was fun to go out there. It was fun to be in that scenario. With the penalty, I thought it would happen.”

The kicker lauded special teams coach Ryan Ficken, who has the Chargers practice the play on occasion.

“Everybody was trying to figure out what was going on,” linebacker Bud Dupree said. “We knew he could make it. We just didn’t understand. Was it going to be a two-point or three-point, or did we get the ball on the 1? We didn’t know.”

Even without a penalty on the fair catch kick, if the time expires when the punt returner has called a fair catch, the receiving team may opt to do a fair catch kick, although there will be no untimed offensive snap option since there was no penalty.

The last time a free kick field goal was attempted was in 2019 when Panthers kicker Joey Slye missed from 60 yards.

To find the last made one, however, you have to go back to 1976 when Ray Wersching converted a 45-yard attempt, fittingly for the Chargers, then of San Diego.