Form angles with a combination square

[Saltfever]

edit ... B = 3.438 / tan (30) = 3.438 / 0.577 = 5.954 in ~= 3 & 15/16 in.

Love the concept, Marv. But you lost me at the end. What does ~=3-15/16 relate to? Isn't beam length 5.954?