In article ,
"Christian McArdle" says...
I expect you're right but I think (as someone else said) 'blind' would
be easier to understand for 'closed'.

That's also a term I've heard used for closed, but I don't think it is
easier to understand! Blind for me means someone/thing that can't see. And
all grommits are somewhat challenged in the seeing department, AFAICT.

I think you're going down a blind alley with that one ...