This place is locked up tighter than a drum.
4 seconds sound clip from Scooby-Doo, Where Are You! - What a Night for a Knight (S1E1).
You can hear this line at 00:06:39.095 in the Blu-ray version of the episode.
Quote context
[...]
- And hold on to your hula-hoops... It says here made only in England.
- England?
- That settles it. There's something fishy going on in that museum.
- Museum?
- Right, Scoob, tonight we're going fishing.
- This place is locked up tighter than a drum.
- Then, like, how do we get in?
- Easy. Shaggy goes through that window up there.
- Why me?
- Because that's a small window, and you're the thinnest.
- Oh, boy.
- Come on, give me a hand with this ladder.
- Well, if we don't get in, we'll never find out what happened to the missing professor.
[...]