David Kornblum asks:
If Boneh does not apply to utensils, then how can Rav consider wedging a peg into a hoe boneh instead of striking the final blow?
The Kollel replies:
Shab-102.ec1
You are in good company, as Tosfos ask your Kashya. And they answer by differentiating between merely replacing shutters or the pieces of a Menorah together (where we say 'Ein Binyan be'Kelim') and making a vessel from scratch (where Binyan will indeed apply and) which is what Rav is talking about.
Be'Virchas Kol Tuv,
Eliezer Chrysler