The rank of lieutenant colonel is usually awarded to the appointed constable, steward of defense, marshal or other such official of a ducal court. Like all lieutenancies, it is intended to be understood as a stand-in holding “in lieu” of the colonel of a regiment, which in most cases is a duke. The one whom he selects as his lieutenant is usually the greatest and most influential of his territorial barons or counts; it is best if the appointee has both a company and a retinue of his own.

The rank is not recognized by letters patent, so the position is affirmed by the award of a commission of array, which also connects the office of the Lord Constable with the regional, ducal office of the constable in charge of defense for the particular duchy.

In the Navy, the equivalent rank is commodore, and it is not only a lieutenancy to the admiral of the fleet, but also bears direct command of a smaller subsection of the fleet called a flotilla.