Buzz Aldrin wasn't the first to McGuyver a solution to a difficult problem, but his use of a felt-tip pen to activate a broken circuit breaker to enable the Eagle to blast off from the moon surely ranks as one of the most dramatic.
As recounted in his book Magnificent Desolation, Aldrin and his moon-walking companion Neil Armstrong were gathering themselves into the landing module to start the return home when he noticed something lying on the floor. It was a circuit breaker switch that had gotten bumped and had broken off in all the too-ing and fro-ing in the cramped environment.
As luck would have it, this wasn't just any old switch: it was the switch to the circuit breaker that activated the ascent engine that would lift them off the moon to rendezvous with Mike Collins, who was orbiting overhead in the Columbia. If they couldn't get that breaker pushed back in, they'd have to figure something else out, or there'd be no ascent.
They told mission control and then tried unsuccessfully to catch some sleep. The next morning, no solution was forthcoming so as Aldrin relates in his book:
"Since it was electrical, I decided not to put my finger in, or use anything that had metal on the end. I had a felt-tipped pen in the shoulder pocket of my suit that might do the job. After moving the countdown procedure up by a couple of hours in case it didn't work, I inserted the pen into the small opening where the circuit breaker switch should have been, and pushed it in; sure enough, the circuit breaker held. We were going to get off the moon, after all."
Mike Collins donated his own felt pen to the Smithsonian National Air and Space Museum which he helped found.
Aldrin held on to hisand keeps it with the broken breaker switch.