Originally Posted by Kapusta

Most (if not all) lockouts these days lock the shock at its most extended point. They lock the compression circuit, so the fork/shock cannot compress, but it can extend. So basically it ends up at max (or close) and stays there. So if you engage the lockout with 30% sag it will stay there if you don't move at all. But as soon as it extends to 20%, it will lock there, and so on.

So no, you generally cannot choose a position to lock the shock in. Closest I think you could get would be a shock/fork with travel adjust, and then lock it.