When marking with a knife or pencil, layout lines can be transferred around a corner from one surface to another easily and precisely using an ordinary steel square. The 1-1/4" by 2-1/4" legs of this small aluminum square wrap right around 90 corners, letting you mark with a pencil nearly as precisely as with a knife. The large saddle square is 1-1/2" wide so the marks will fit nominal 2" lumber, and has a slot machined through the center to help lay out stud locations.

This square tipped on its side can also be an effective drill guide to make sure the is entering the wood square in both directions.

from $18.99