I wonder if we're talking about 2 different things here.
The OP was talking about sewing triangles onto blocks. She called them "setting triangles", which is the terminology usually used for the triangles used at the ends of rows of blocks set on point:
[ATTACH=CONFIG]513705[/ATTACH]
However, I read her post as asking for advice about sewing this:
[ATTACH=CONFIG]513706[/ATTACH]
SandyG, do either one of these illustrations help?