The following entry appears on pp. 79-80 of “The Book of the Chapter” by Albert G. Mackey.

The Day Set Apart for the Celebration of the Cape-Stone of the Temple.

The Cape-Stone, or, as it would more correctly be called, the cope-stone, (but the former word has been consecrated to us by universal masonic usage,) is the topmost stone of a building. To bring it forth, therefore, and to place it in its destined position, is significative that the building is completed, which event is celebrated, even by the operative masons of the present day, with great signs of rejoicing. Flags are hoisted on the top of every edifice by the builders engaged in its construction, as soon as they have reached the topmost post, and thus finished their labors. This is the “celebration of the cape-stone”—the celebration of the completion of the building—when their tools are laid aside, and rest and refreshment succeed for a time to labor. This is the event in the history of the temple which is commemorated in this degree. The day set apart for the celebration of the cape-stone of the temple, is the day devoted to rejoicing and thanksgiving for the completion of that glorious structure.

Masonic teachers have not agreed in determining what was the particular stone referred to in this degree. A few suppose it to have represented the last and highest stone placed in the temple. If this were the case, the Mark Master’s keystone would be very improperly made use of on this occasion, for it by no means represents the highest stone of the temple. A majority of scholars have, however, adopted the more consistent theory that the keystone was appropriately used in this degree, and that it was deposited on the day cf the completion of the temple in the place for which it was intended, all of which relates to a mystery not unfolded in this degree, but reserved for that of Select Master. In either case it was a cape-stone—in one, the cape-stone of the whole, temple; in the other, only of an important part of it.

In my own recollection, a promise of secrecy was exacted of all Most Excellent Masters respecting the place where the keystone was deposited, and, although this usage has now very generally been abandoned, I have the most satisfactory reasons for knowing that such a promise constituted a part of the original Obligation of the degree.

The full text of Mackey’s monitorial instructions on the Most Excellent Master degree may be found at:

Most Excellent Master from Mackey’s “The Book of the Chapter”