Tail cone access
I didn't have to crawl into the tail cone of a 707 jetliner often, but when I did, it was a worrying experience. Newbies like me were told of a story in which an aircraft mechanic was stuck in the tail section after someone had replaced the access panel without checking to see if anyone were inside. Nobody heard his banging amidst the noise of the busy JFK airport ramp.
When the aircraft began taxiing, the mechanic got out his wire cutters and cut the safety wire on the electrical connector for the jackscrew motor assembly. When he disconnected the connector, the cockpit crew noticed the "fault" and returned to the gate.
Here's a photo that shows the tail cone access with its panel removed. It's the nearly square hole just below the center of the photo. When I had to crawl into it to work on the electronics (typically a yaw damper component, if I recall correctly), I hung a bright red ribbon from the opening.