That's right, it'll lock itself off.
4 seconds sound clip from the Jaws (1975) movie soundboard.
You can hear this line at 01:42:44 in the Blu-ray version of the movie.
Quote context
[...]
- I'm going to back her off now.
- You watch those barrels, boys. Watch them.
- All right, gentlemen, snag them.
- Now then, tie them to the stern cleats.
- Brody, bring your end around the cleat.
- That's right, it'll lock itself off.
- Stand away from those stern cleats!
[...]