Look at the first stanza
Between my finger and my thumb
The squat pen rests; snug as a gun.
This in context with the whole poem, almost outlines the theme. The word squat is very important. To many people it means different things. Once I read the poem, I thought that it almost reminded me of a squatter and then I thought of how to link that with the poem. I thought that it was as if the pen has found him, like a squatter finds an empty house etc.
It then goes on to say 'snug as a gun' this shows comfort. It shows that his pen is powerful and that writing can bear as much fear and power as a gun and also shows that writing is not inferior. - this shows a metaphorical theme instantly.
Under my window, a clean rasping sound
When the spade sinks into gravelly ground:
My father, digging. I look down
Heaney uses onomatopoeic language to show imagery. The word 'rasping' gives a strong sense of imagery and it is easy to see what he wants us to see.
The third line indicates that he is reminiscing, looking down at his father. All poets choose their words carefully and he has specifically mentioned that he is looking down at him. Yet throughout the poem there is a clear outline of great admiration for his father and his grandfather- he says
By God, the old man could handle a spade.
Just like his old man.
Till his straining rump among the flowerbeds
Bends low, comes up twenty years away
Stooping in rhythm through potato drills
Where he was digging.
This is, to me, the most confusing stanza. So my analysis is not very good :(
I think this is almost as though the poet is writing a lot about a little to show and emphasise his respect for his father and grandfather
Stooping in rhythm shows a repetitive sense to the poem, but it also shows quite an enjoyable sense to it. Depending on your view, either is fine.