It is first mentioned in the opening of the Lodge. Many modern dictionaries have definitions and as an example Chambers 20th Century Dictionary states:
COWAN, [‘Kow’an] (Scot) n, a dry-stone diker: a mason who never served an apprenticeship: one who tries to enter a Freemason’s lodge, or the like, surreptitiously. [origin doubtful] read more…
I was born in antiquity, in the ancient days when men first dreamed of God. I have been tried through the ages, and found true. The crossroads of the world bear the imprint of my feet, and the cathedrals of all nations mark the skill of my hands. I strive for beauty and for symmetry. read more…
When it’s a whisky jar! or at least a representation of one. The one shown here is a pottery maul and is used by the Master at the Harmony. The Harmony, known as the Festive Board in England, is held after the Lodge has been closed and usually consists of food, drink, toasts and entertainment. The exact nature of the Harmony varies from Lodge to Lodge. Some are formal with a specific sequence of toasts etc. but other are informal.
The pottery maul is usually in the charge of the Master as it is his emblem of power and authority both in the Lodge and at the Harmony but sometimes this is delegated to the Chief (Senior) Steward or sometimes the D of C.
So what is the pottery maul used for? It is certainly not for calling the Brethren to order as the contents are too precious to risk banging it.
Source: The Grand Lodge of Scotland.