2. Quite possibly it is the same idea as that in old Egypt:

(Reference: Wilkinson)

At left the goddess of dawn raises the sun up and at right the goddess of evening (with face down) takes care of the descending sun.We can infer that the two holes in pu glyphs alternatively can be regarded as the blinding light discs of the morning and evening suns.

Yet, the holes are there. To combine the two alternative readings it seems necessary to regard the sky region behind the sky 'roof' as a region of flames.

The East Polynesian concept of sunlight resembling lifegiving water (vaiora a Tane) then will give rise to further ideas:

"... Now the deluge was caused by the male waters from the sky meeting the female waters which issued forth from the ground. The holes in the sky by which the upper waters escaped were made by God when he removed stars out of the constellation of the Pleiades; and in order to stop this torrent of rain, God had afterwards to bung up the two holes with a couple of stars borrowed from the constellation of the Bear. That is why the Bear runs after the Pleiades to this day; she wants her children back, but she will never get them till after the Last Day." (Hamlet's Mill)

Holes can be plugged. Maybe this explains why there are instances, in the rongorongo texts, where the parallel glyphs are without holes, e.g.: