Plot all measured surfaces (plane) on a stereonet. These diagrams are basically the same, plotting the planes is a bit easier and includes a couple less steps. Plotting the poles requires extra steps, but is better when you have lots of measurements.
The intersection is the fold axis. It should have a trend and plunge
Use the fold axis to project the map onto the fold profile plane
You will project in the direction of the trend and project (or shorten) by \( \sin \) plunge
Plot the limbs of the fold (also plot the poles to the planes) Red and Blue Lines
Determine the fold axis by the intersection of the limbs. What is the trend and the plunge
Plot the poles to the planes for each limb, Red and Blue points
The interlimb angle is \( 180 - \theta \) where \( \theta \) is the angle between the poles to the limbs / planes. Measure this angle along the great circle
The Axial plane goes through the fold axis and the the point halfway between the poles to the planes / limb