Getting in the groove...

Sharp Chisels and Mikey-Mike scratched their heads to get around this compact joint.
To put you in the picture, there is a post shown with a long haunched tenon going through the tie-beam into the principal rafter above it.

All three joints come together and are secured with hard wood 19mm pegs which are driven through the joints.

As you can see from the pictures the tie-beam (horizontal timber) has 38mm mortises chopped into it ready to receive the arched knee brace

Left hand knee brace template positioned on the frame