You are describing the mast.
A mast
mast
mast
An upright pole on a ship to support sails or antennae.
Yes.
The mast.
Mast
The mast.
why cant it be pole.
The sternmost rigging pole on a ship is typically the mizzenmast. It is located at the aft or rear of the ship and is used to support the mizzen sail.
Perhaps you are referring to the mast.