here's another fool proof method..
just set your ratchet on 'undo' ( for normal right hand threads ) ..
then whether upside down or not ..
the ratchet will only unscrew.
 or use that as a tool to tell which way is unscrew.

----- Original Message -----
From: "Mike South" <msouth@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, March 06, 2011 5:28 PM
Subject: Protip: beyond righty tighty lefty loosey

> So, what follows is quite possibly the best thing I got out of my physics
> degree.  When you wrap the fingers of your right hand around a wire with
> the
> thumb extended (like in a thumbs up gesture) and the thumb pointing in the
> direction of the electrical current in the wire, your fingers show the
> direction of the magnetic field that is induced around the wire.
>
> Which was valuable to me for some brief period of time when I had to draw
> my
> vectors in the right direction on an exam.
>
> However, it also works for (right-handed) screws, nuts, bolts, etc.
>
> So if you're under the van* reaching up to a bolt that's pointing down
> toward you and you have no idea which way is which, just wrap your right
> hand around the bolt with your thumb pointing the direction you want the
> bolt to move.  Your fingers will point in the direction that you should
> turn
> the bolt in order to make it go that way.
>
> Or, if you've got the wrench on and you're tugging and having a moment of
> doubt, you can curl your fingers (right hand only!) around the bolt in the
> direction you are turning your wrench, and your thumb will tell you which
> way the bolt will move once the penetrating oil finally kicks in.
>
> mike
>
> * vanagon content!  (But seriously, this came up because someone mentioned
> it in the discussion about getting the bolt off that holds the spare in.)