beam construction help please

[MountainDon]

I drew lines around the assembled beam with a speed square. Then I cut all 4 sides as deep as I could with the circular saw. I finished the cut with a reciprocating saw. A hand saw would do the job as well.




That's how ended up with a virtually perfectly square floor.  


I also use the speed square as a cut guide. Sometimes like for this, I clamp it in place. I have the amount of the left and right offset written on the saw shoe so I don't have to measure the blade offset each time or rely on memory.  

[Squirl]

Looks like quality work.