Summary

Missing one of the railing attachment pieces. STEP file provided for you to modify.

Designed to use 3/8 inch dowel rods. Dowel rods get secured in place with small screws, short #4 screws should work. You could also glue them in place.

Most of the angles are in 30 degree increments. The top leg is 30 degrees below horizontal. The lower legs are 30 degrees away from vertical. The angle between the two lower legs is 32 degrees (this is the angle I needed for them to align with the railing balusters).

The STEP file has user parameters that will let you easily change these angles.