This is what is actually inside the top of the flag pole
Hopeful NCOs at leadership schools or promotion boards are asked a two-part question: The first part is, "how many trucks are there on the military installation?" The answer is: one. 'Truck' is the term for the finial — or ball — on top of the base headquarters' flag pole. It's kind of a trick question because every other 'truck' is either a military or privately-owned vehicle. The second part of the question is, "What's inside the truck?"
The answer the Sergeant Major and First Sergeants are looking for is, "a razor, a match, and a bullet." Occasionally, it's also said to contain a grain of rice or penny — it depends who's asking. The actual answer, and one they probably won't accept, is "absolutely nothing."
The items that are supposedly inside the truck are to be used in the case of an enemy invasion. If the enemy overwhelms the base, it's up to the last survivor to climb the 50-to-75-foot pole, unscrew the truck, strip the flag with the razor, give it a proper retirement with the match, eat the grain of rice for strength, and blind the enemy with the penny. The survivor then digs up the pistol buried six paces away from the base of the pole.
What the survivor is supposed to do then is up for speculation. If you don't use the gunpowder for kindling, the most universally accepted use of it is for the survivor to turn the pistol on themselves in a last-ditch, you'll-never-take-me-alive act.
Here's the thing, though. The military is very particular about the order of precedence when it comes to the Stars and Stripes. No flag can fly higher than the American flag. There are two exceptions to this rule: "Death's flag," or the flag that is raised, in spirit, above the actual flag when it's at half mast (but is actually nothing) and a chaplain's pennant (which is a pennant, not a flag).
Placing a chaplain's pennant higher than the American flag is to say that the only thing higher than country is God. The fact that some claim we'd put a bullet in the finial above even the chaplain's pennant is a dead giveaway that this myth is BS.
The final nail in the coffin on this myth is the fact that there's no regulation set by the Department of Defense, by any branch, or by any military installation. As widespread as this belief may be, there simply isn't any written record of it in any official capacity.