The point of the Killing House is to train the SAS operatives to enter a room and be able to assess the situation and shoot any threats.
The building has special rubber-coated walls to absorb bullets, extractor fans to clear out fumes, and video cameras in corners to record the action in the rooms.
The SAS also use the Killing House as part of the training members of the British royal family receive for hostage situations.
Each royal and their partner is provided with black overalls, marked with "his" and "hers", where they then play the role of "hostages" and are put in a room in the Killing House surrounded by targets of cutout "terrorists" while the SAS conduct a live fire exercise to rescue them.
Prior to the exercise he signed a humorous letter that remains on the wall at Stirling Lines:“Should this demonstration go wrong I, the undersigned Prince of Wales, will not commit B Squadron 22 Special Air Service Regiment to the Tower of London.