The directors were used to house the optical instruments use to measure distance between the ship and its intended targets and to direct the ship's guns to them. They also house its crew and protected them with light armor from sharpnels. A number of small ports can slide open to admit fresh air. These directors were usually located higher up (i.e. on top of the bridge) to increase the distance which they could spot the targets and to give them a clear view of the targets.

The principle of operation was simple - the operators sit in approximately the middle of the director and looked through a binocular device. The images to this device were channeled from the outside through the two optical ports on the extreme two ends of the rangefinder via prisms. Since the images came from two locations far apart, the images will only superimpose with adjustments to the prisms. The closer the object was, the more adjustment was needed since the path of the light between the object and the two rangefinder optical ports was less parallel. By calibrating the degree of adjustment initially with objects of know distance, the adjustments during use can be use to determine target distances. By definition, the farther apart the optical ports (i.e. the bigger the rangefinder), the more accurate they were. In actual use, the adjustments of the rangefinders were coupled to the elevations of the gun barrel and movement of the turret left and right affected the traverse of the gun mounts - thus the name director.