Originally Posted By: Ian
There are plenty of instructions on the internet, basicly hold a powerful magnet close to the needle the correct way round which is the trick.


Alright, I found this (from <http://cse.ssl.berkeley.edu/segwayed/lessons/exploring_magnetism/exploring_magnetism/s1.html>):

Quote:
Caution: Compasses can easily change polarity using magnets
It is fun to use the bar magnet to make a compass needle rotate around. However, if while doing this the needle does not move, the polarity (north and south locations) can be reversed. To make the needle point in the correct direction, the polarity of the needle must be such that the arrow points toward Earth’s geographic north when standing outside away from electricity and other magnets. In order to reverse the polarity of the compass needle in a controlled fashion, hold the compass so the needle is horizontal. Then take the bar magnet and move one pole of the magnet length-wise across the compass needle, making sure the needle does not move.


This last part about making sure the needle does not move may be a problem for a compass one cannot open, such as a keychain compass. I'll try to hold the compass vertically so as to immobilize the needle against the side. The instructions above say to hold the needle horizontally, but I don't think that's significant. We're just reversing the polarity on the magnetic field of the needle. We don't have to line up the needle with the earth's magnetic field. Will let you know the outcome. May still buy the Tru Nord.