Quote Originally Posted by chasem View Post
It's much easier to look at the actual tartan. it's easier to visualize the pivots than to calculate them with the thread counts.
Maybe only if you are taking the thread count yourself and have to figure out where the pivots are, but in that case you are startiung with a peice of cloth anyway, so the question is a moot one.

But if you are looking at a recorded thread count, the pivots will always be the first and last numbers listed, so no calculation is necessary.

The MacNaughton, for instance, is:
K4 B4 R52 B26 K26 G50 R52 B4 K4

In this case, both of your pivots are K4 (four black threads). To further confuse maters, the are both also bordered by four blue, and 52 red. So if you are starting with either pivot and working your way towards the center of the pattern, it looks the same until you get to those middle three elements, which are going to look different depending on your direction.

Really, what we have here is a typical symmetric tartan, with two pivot points. It's just that those pivots look very similar, which can lead to confusion if someone isn't looking carefully.