I believe that what we see here 'hacking at the sun' is a very old type of adze, made in one piece and of bone:

This weapon possibly 'kills' (or 'wounds'?) the sun at zenith. After noon we no longer see the true sun, just a poor image of himself. But at the same time I remember the sun-beam in form of a pole-axe in Mnajdra (like the Egyptian hieroglyph neter, god).

Anyhow the 'breast glyph' probably refers to summer, because that story is told by the glyph immediately following: