Figure3-13.—Telescoping tram bar and related equipment.
BENCHMARKS
Benchmarks are small metal plates that contain an
engraved cross. The plates are either brazed or welded
to some rigid portion of the ship’s structure at a posi-
tion where the engraved cross can be sighted on with
the reference element (director). A benchmark maybe
engraved on a flat plate for bulkhead mounting or on
a block with an inclined surface so that the mark is
clearly visible on the ship’s deck. Benchmarks are
reference marks used in alignment to establish the
angular relationships (elevation and train) of an ele-
ment’s line of sight to the ship’s structure. When an
element is sighted at its benchmark, its dial readings
should agree with recorded values. If there is dis-
agreement, alignment of the element is necessary.
Figure 3-14 shows two typical benchmarks.
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