OK -> None of the experts bit!
I'll go ahead

Using Wallace as the example:

Sett- 1/2 yellow to yellow-> black on red to yellow on black

Repeat-> Sett PLUS the reverse-> What is repeated in full
(This is the stripe to stripe)

Yes, it was the Wallace that I bought (Great-Great Grandmother was a Wallace-> married a Neel and their daughter married a Wilson, whose daughter was my mother).

I was told a 3 inch sett (which it is not) When it was recieved, I though-> "That don't look right!" I measured a 1.5 inch sett and the full repeat of 3 inches.

This particular sett will work in a box pleat of a 3 inch box pleat-> sett for a full repeat. I plan to use 3 repeats to make it work. Not what I would advise, but it is good practice, I have no other use for the fabric, and it will look good in the end. Actually, not to far off historic portraits.

On almost ANY other tartan, this would not work. On all of my other tartan fabrics and ANY Black Watch based pattern (inc. my own MacNeil) it wouldn't be usable! Yet, on Wallace it will.

All readers-> Members and Lurkers:

Beware of the terms used by fabric merchants! The ones that specialize in tartan SHOULD know their correct meaning. Others, however, use them incorrectly at times. Make sure you ASK for a measurement of center stripe to the SAME center stripe accross a FULL repeat.