Peeking at the contents of a mount point

[Kevin O'Gorman]

I recall some time ago seeing a command -- a variant or argument to
'mount' I think -- which allowed you to see the real contents of a
mount point while something else was still mounted on it.
I've looked back through 2 years of postings and can't find it.
Anybody have a clue?

-- 
Kevin O'Gorman

programmer, n. an organism that transmutes caffeine into software.