Traveling trunnion hole b, in some artilleries, that trunnion hole in the gun carriage, in which the gun barrel rests during the march; going into action, the gun barrel is transferred to a second trunnion hole, the fighting trunnion hole a, for this purpose. The traveling trunnion hole is only needed on very curved carriages, and its use has the disadvantage that the Capsquares become loose if the gun barrel is frequently removed from the fighting trunnion holes. When this happens, the trunnions are no longer held in place firmly, which inevitably results in inaccurate shots.
Source: Rumpf, H. F.: Allgemeine Real-Encyclopädie der gesammten Kriegskunst (Berl. 1827)