This is one of the great movies of all time.... on par with = The Graduate = .... It had a major influence on teenage girls who saw it in the '60's.
We constantly joked about the guys we had locked up in our own attics! Of course, it was the other way around... Each girl had 7 or 8 guys locked in her attic, and the fact that a couple of us actually had bedrooms in the attic made the joke even funnier.
I don't know why I have not seen this film since it came out in 1968, but I really wish someone would bring it back.
Even to this day, my friends and I joke about our attics, in the same way that we joked about the Ford that was mentioned in The Graduate (of course, that reference didn't last quite as long as the "attic".)