Where did he get a saw there?
Awww poor Nole.
I'd like to know this too lol.
I don't know is he really sawing his rackets, but this can help:
He didn't stay in Olympic village - he, and whole Serbian tennis team, have rented houses near Wimbeldon complex.
And I think that every house have some kind of saw in garage or in some tool shed. So possibility to have saw is very huge... but as I said, I don't know is he really doing that.