hello everyone tonight

Ken I am not much good at posting sketches but with a little imagination I will try our best to clarify

The sides run at angles separated by a 6" spanner, I noted that the !" bolt will run in a channel located in the spanner.

I decided to use the channel as a guide for boring the holes through the exterior vertical timber walls

Knowing perfectly well that there could be some error I decided to use a slightly larger diameter auger, and a good thing I did because the ship augers are famous for not boring really straight, at least that is my observations from experience

The auger did wander a bit even after carefully lining up , and carefully sharpening before I used it.

I hope this helps