Related Clues:
- Flow controllers
- Lights-out signaler
- They're faucets in America
- Military signal and faucets
- Military signal to turn the lights out
- Military signal for lights out
- 'Knocks, on the door say (4)'
- It causes lights to go out
- For water and lights out, by the sound of it
- That's the way one knocks this back a yard
- They may be turned on for lights out in the US
- At the end of the day they get turned on for the American serviceman
- They sound as if they get the lights knocked out in the USA
- Water did be spitting from them up the last thing at night
- Turn them off and turn the lights off in the US army