Let's see, I'm a smart guy, I can make this work...
The combination square is still a propper angle of 90 degrees and a Right angle. The ability to travel along a Perpendicular shows that a Mason can still be virtuous while adapting as a situation requires thus providing Depth to an otherwise two dimensional tool.
The backside of the Right angle on a combination square is a smaller angle of only 45 degrees. This represents the junior, or neophyte, Mason who is not fully versed in the manner of maintianing the correct Right angle. Wherever the proper Upright Mason goes, the Apprentice follows and learns the Right.
How's that work? LOL