Det var en servicelucka "
- Från filmens skript
WIDE SHOT as Rey holds on carefully as the guards walk off, not seeing her over the edge, a death drop below her.
But then she SEES SOMETHING and has a brainstorm. She strenuously cross-climbs to an invisible SERVICE HATCH, which She opens, and climbs INSIDE THE WALL, closing the hatch behind her.
Working her way sideways, hand over hand, while methodically locating shallow footholds, she made it across to a service hatch slotted into the wall of the atrium. It opened, silently and without the need to enter a code, at her touch. While still yawning to depths unknown beneath her, the inner workings of the base that she was able to reach through the hatch provided access to better handholds. If she was lucky and didn’t lose her sense of direction, much less her grip, she felt she might be able to work her way across to the corresponding service area that ran underneath the TIE fighter hangar, avoiding the guards above. Then she would have to find a way to access the hangar deck itself and without drawing any attention. Assuming she could do so, she could try to steal a fighter.