What does Marty wear to protect himself from being shot in "Back to the Future III"?

In “Back to the Future Part III,” Marty protects himself from being shot with a metal door from a stove. He ties the heavy iron stove door beneath his clothing and uses it as a makeshift bulletproof vest during his showdown with Buford “Mad Dog” Tannen in 1885.

The trick is inspired by Marty’s knowledge of Western movies, especially the kind of improvised armor seen in old frontier and gunslinger stories. When Tannen shoots him, Marty is knocked backward, making the scene appear fatal for a moment. He then reveals the stove door, turning the apparent shooting into one of the film’s comic reversals.

The scene also echoes the first film, in which Doc Brown survives being shot by Libyan terrorists because he wears a bulletproof vest after receiving Marty’s warning letter. Unlike a modern ballistic vest, the stove door is an improvised piece of cast iron; the movie uses it for comedy and adventure rather than realistic firearms protection. Marty later uses the same door offensively, striking Tannen with it.