- "Marty waited a minute. Once they [the Biffs] were away from the garage, he would get out of the car and follow them. / Young Biff stepped back in front of the doorway. Marty ducked down. He heard a creaking sound, like old hinges complaining. It was getting much darker in here. / Marty risked another look. Biff was closing the garage doors! The two doors slammed together as Marty lifted his head to watch, followed — immediately — by a heavy click. / Marty didn't like the sound of that click. / He got out of the car and moved to the doors. He tried to tug them open, but they wouldn't budge. He pulled harder, hoping they were stuck, but they didn't move at all. They weren't stuck. Biff had locked them. That click meant there was a padlock on the other side. / He looked around the garage. The windows were tiny. They let in hardly any light at all, and they were too small for even a child to get through. Marty was trapped in here!"
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 155)
Biff's garage was attached to his grandmother's residence on Mason Street in 1955. Biff parked his Ford Super De Luxe Convertible there when he was at home. There were two wooden doors of the garage that opened outward and could be fastened with a conventional lock. Each door had four small square windows.
When Old Biff encountered his younger self, he drove him back to the house and into the garage, both unaware that Marty McFly was in the back seat. Inside the garage, Old Biff revealed the Grays Sports Almanac and tested its validity by tuning into a radio station for a football game between Washington and UCLA. After Biff handed the book over, they both walked out of the garage and young Biff locked the doors, with Marty still inside. Marty ran to the doors to find that they were still locked.
Marty called Emmett Brown on the walkie-talkie, saying that he had been locked in. Doc could not risk bringing the DeLorean time machine out into the open during the day and had to wait until dark to rescue him. Later that night, Biff left for the Enchantment Under the Sea dance and Marty hopped back into the car. Biff drove out of the garage and towards Hill Valley High School. When Doc arrived by bicycle at the house and the garage, Marty had since disappeared. Marty would later contact Doc from the car just as they were about to enter the River Road Tunnel.