Trunnions

The two round projections on the sides of a piece of ordnance by which it rests upon the carriage and affords means of elevating and depressing the piece by its oscillations in the grooves on the upper edges of the cheeks of the carriage.

Gauge. An instrument by which the diameter of the trunnions is measured.

Ledge. The small shelf to the trunnion of a heavy piece of ordnance.

Level. The spirit-level by which the trunnion ledge is placed in a horizontal position.

Plate. The plate which covers the upper part of the side-pieces and goes under the trunnion.

Ring. The ring upon a gun just forward of the trunnions--now obsolete.

Rule. The rule employed in measuring the distance from the base ring to the trunnions.

Square. The instrument made use of in ascertaining whether or not the axis of trunnions is perpendicular to the axis of the bore.