It's known as the immovable ladder because it is understood that no cleric of the six ecumenical Christian order may move, rearrange or alter it without the consent of all six orders. The ladder is made of cedar wood and it was first mentioned in 1757; it has remained on the side of the Church of the Holy Sepulcher since at least then.
The ladder has some symbolism. Pope Paul VI ordered in 1964 that the ladder will remain in place until the Catholic Church and the Orthodox Church reach a state of ecumenism, That is, when both churches reunite as one.
Despite the moniker, though, the ladder has been moved a couple of times. Once in 1997, it went missing for weeks and it was thought that it was moved on a prank. In 2009 it was moved to the side against another window for a short period of time.
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