sleep round the clock—sleep for twenty-four hours:
- The climbers, when they returned, were so tired that they fell into bed and slept round the clock.
Note: The expression does not correlate in meaning with the phrase sleep around—have sexual relations with many people:
- As far as I could discover, he had no reputation for sleeping around.
sleep through the clock—fail to be woken by a clock:
- I’m sorry I’m late, I slept through the clock this morning.