Depends on the situation and the brace size and what kind of material I'm using. It doesn't really matter. The legs are measured on reference faces and located on whatever face they need to be (using a Big All or machinists square for the housing depth, off of reference).
If brace leg is 42", then it is 42" relative to the reference face of the timber it is going into.
So for square rule (and I do not model the reductions in my drawings) a 42" brace is marked 52" down from the top (reference) of an 8x10 tie on the post.
If I am laying out the tie it is 42" from the edge of the diminished housing. (where 2 perfect timbers would meet).
If it is going into a full housing (on a girt, for example) it is still 42" from the theoretical 8x8 timber, and 42" + housing depth from the shoulder of the tie.
