Siege Ladders
It’s difficult to invade a medieval city, especially if the objective is protected by a high wall with crenellations and defending archers. To scale the walls and overcome the defenders, the invading army employed siege ladders. This was not always easy because it was challenging to ascend the ladder without being struck by incoming arrows.
The director shouts instructions to the actors as they climb the siege ladder, and the sound guy records their conversation with his boom microphone. The actors probably did the scene and climbed the ladder several times throughout this take to ensure they got the best shot.