Old style truss rod - up or down?

[tdq]

I've just done a bolt on conversion on an old beater I got cheap. It has an old style truss rod - just a nut on a metal rod. The adjustment nut is at the headstock end. As I've moved the neck back and forth to test the angle, the truss rod may have rotated in its slot and now I'm not sure which way it was in originally - facing up or facing down (there is no way of telling up or down - it's just a rod with a nut on the end!) Before I reglue the fretboard, does this actually matter? I've done some tests but not 100% sure of the results. When I tighten it, will it always bow the neck up, regardless of how it sits? I worry that it might bow the neck in the wrong direction as I tighten it. Or will it always bow in the path of least resistance, i.e towards the fretboard?
Hope that makes sense and any advice would be appreciated.

[Truckjohn]

Most of these had some bend in the middle. They weren't just a straight rod in a straight channel. The bend corresponded to a hump in the shim under the fretboard. The little dog let in there creates the down "pull" on the headstock. Or at least that's how it is supposed to work.

Thanks

[LouieAtienza]

If it's just a single rod, then no. If I remember correctly, Gibson actually bowed their trussrods the OPPOSITE way Fender did. Either way doesn't matter, even dead straight works, if it's low enough.

[Bruce Sexauer]

It is hard to imagine how you could have rotated it as the far end is supposed to be anchored solid and unable to turn. Both common concepts share this anchor aspect. Gibson is the only maker I know of that used the so called compression system. Others, myself included, used the high at the ends low in the middle system which operates on the theory that the shortest distance between two points meant that as the rod is tightened it will straighten, and be stronger than the neck wood forcing it to bend against the string tension. The modern double rod systems do weigh a little more, but they are far more effective and reliable.

[tdq]

It's definitely rotatable but the "motionless" lug it sits in can only sit one of two ways and I can't see an obvious marker. In hindsight I should have payed more attention but it's all part of the learning process. I haven't take off the whole fretboard (just the part above the neck join) so I can't see if there is a hump there. It's an old brandless 12-string I got cheap which I thought I'd attempt a neck reset on - a bit of a hackjob on my part but it seems to have worked, functionally. Anyway I'll soldier on, thanks all for the info.