(Semi-spoiler alert. I've read up to page 310. Ron has just left.) Kids, will you stop fighting! Get along! Discord is what V wants!
I reckon the sword is inside the snitch. They should be on top of Extension Charms by now. But how to open the snitch? "Opens at the close"? Is "the close" a place? I think there's a play on words here. Isn't a close a place, esp. in British English? Something to do with a cathedral or an abbey?