The third ogham family cuts its strokes across the line at an angle, and nGetal takes three of them.
How the letter is formed
nGetal is the third letter of the third family, Aicme Muine, and is cut as three parallel strokes crossing the line obliquely.
The value is not settled
The manuscript tradition gives this letter the value NG. Whether that was its value in the language of the inscriptions is a separate question, and the answer is not agreed. The letter is rare in the surviving corpus, which leaves very little material on which to test any proposal, and the reconstructions on offer depend on assumptions about the shape of Primitive Irish that are themselves debated.
This atlas records the manuscript value as attested for the manuscript period and records the earlier value as open. What would settle it is new epigraphic material: a stone bearing this character in a word whose etymology is independently known. Such a find is possible rather than likely, since the corpus grows by a handful of stones in a generation.
In the corpus
The orthodox inscriptions are almost all personal names in the genitive, cut on standing stones in Ireland and in Irish-settled parts of Britain, dated on linguistic grounds to roughly the fourth to the sixth centuries.
The reed attached to this letter comes from the manuscript glosses and is treated separately here, as is the modern calendar material.