This type of glyph could perhaps show three 'stones' (tau) - cfr Tau-toru as a name for the Belt stars in Orion. Where two of these glyphs are found together, we could then guess it might indicate Tauono (six stones) = the Pleiades.

In this text I will - as a starting point for the discussion - assume that each one of these 7 such double glyphs ought to represent Tauono.

The asterism of the Pleiades, when located in the sky at a specific point during the night, would determine the day in the year. And everyone would have known whether Tauono was above (i nika) or below (i raro). For the Pleiades cluster was the birth-place of the planet Mars.

We can compare with the perception of the Southern Cross (the Crux constellation):

... Whittier said, in his Cry of a Lost Soul: 'The Cross of pardon lights the tropic skies'; which is correct for our day, as it is not now entirely visible above 27º 30' of north latitude. It was last seen on the horizon of Jerusalem - 31º 46' 45'' - about the time that Christ was crucified. But 3000 years previously all its stars were 7º above the horizon of the savages along the shores of the Baltic Sea, in latitude 52º 30' ...

Von Humboldt adds: The two great stars, which marks the summit and the foot of the Cross, having nearly the same right ascension, it follows that the constellation is almost perpendicular at the moment when it passes the meridian. This circumstance is known to the people of every nation situated beyond the Tropics or in the southern hemisphere.

It has been observed at what hour of the night, in different seasons, the Cross is erect or inclined. It is a time piece, which advances very regularly nearly four minutes a day, and no other group of stars affords to the naked eye an observation of time so easily made. How often have we heard our guides exclaim in the savannahs of Venezuela and in the desert extending from Lima to Truxillo, 'Midnight is past, the Cross begins to bend' ...

According to Vanaga:

Tau = 1. to hang; 2 to perch (said of chickens on tree branches at night); 3. tau kupega, rope from which is hung the oval net used in ature fishing. 4 rock on the coast, taller than others so that something can be deposited on it without fear of seeing it washed away by the waves; hakarere i ruga i te tau, to place something on such a rock

Ta'u = 1. year. 2. he-hoa ite ta'u, to confess to a crime committed long ago, by publishing it in the form of a kohau motu mo rogorogo (rongorongo tablet).