Now that the rangetaker is sure of his targets he sets up his equipment.

He uses a Barr & Stroud Rangefinder No 12 Mk III, an optical instrument that measures the angle of light beams that leave the instrument. That in relation with the base length gives him the exact range to an object in distance. In this case he is reading the range to an appointed target line.

Once he measured it about four times and calculated the mean, he passes his result to the fire controller. The sergeant can now start with laying the guns, for this purpose he has a Director No9.
To obtain such alignment, the firecontroller first positions his director perpendicular with the target line. Thereafter he determines the angles by which the guns should align to fire parallel into their target line.

Once he has zeroed his director on the targetline, he reads the angles back to each gunner.
The gunners set up their dial sights and lay them on the director. Once this is done the director can be replaced with a suitable aiming mark, usually an aiming post.

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