If it's this method you're using:
http://users.skynet.be/jcordon/cockpit/TRTLGal.htm
Download here:
http://www.mycockpit.org/fileshare/s...?e=31&catid=27
it looks like a bearing from a roller skate or a small metal cylinder running in a groove up the shaft of the throttle. It works in much the same way as a piston in the cylinder of an car's engine.
If it's this one:
http://www.mycockpit.org/tutorials/showentry.php?e=35
it looks pretty self explanatory and quite elegant if I say so myself.
Good luck :)