Watch tower (Black Guard)

Did you mean Watchtower (building) north of Yanille? Black Guard Watch tower is a wooden building used by dwarves south of Coal Trucks. During Dwarf Cannon quest Dwarf commander asks the traveler to check the tower guard. Gilob the guard is found dead. The trap door is not open before the start of Dwarf Cannon.

Ladder is used to climb up the tower.