When the Apollo 11 crew prepared to leave the Moon, they found the circuit breaker that armed their ascent engine had snapped off after a bulky backpack knocked it, and Buzz Aldrin pushed it back into place with a felt-tip pen rather than risk putting metal into a live electrical circuit.

After their first moonwalk, Aldrin and Neil Armstrong were back inside the Eagle, attempting to rest before the ascent. Aldrin noticed a small black plastic object on the floor. On inspection, it was the broken-off switch from the engine arm circuit breaker, marked ENG ARM on the panel. That breaker fed power to the ascent [...] The post When the Apollo 11 crew prepared to leave the Moon, they found the circuit breaker that armed their ascent engine had snapped off after a bulky backpack knocked