The phrase X marks the spot means a place is exactly where something is hidden or located. If you are building something or about to plant a tree and marking the place you are going to dig a hole, you might jokingly say "X marks the spot".
This idiom originated from pirate maps, where an X was used to mark where treasure was buried.
This idiom originated from pirate maps, where an X was used to mark where treasure was buried.
We finally found the old well - X marks the spot.