1) A term used by sailors for the jamb of a water-tight door. A water-tight door's opening is about 20 inches above walking surface.
2) A term used by hot-rod enthusiasts for after market items mounted to the bottom of a dashboard assembly. (ie. Tachometers, Nitrous Oxide switches, etc.)
If you can't lift a swab bucket over a knee knocker, you have no reason to be on my ship.
1. I was knackered when I got in from work.
2. After my seventh ejaculation I was well and truly knackered.
3. The teacher caught us smoking and now we're going to get really knackered.
4. I tried to fix my dad's PC but now it's more knackered than ever.