I made a pair of jigs for aligning bi plane wings
Adjustable parallelograms
It accommodates different chord gaps and chords. Great for setting up interplane struts between the wings.
Attaches to my magnetic building board with four permanent magnets per parallelogram. All of my building is done on a magnetic board, so this had to match that.
I attempted to make on out of steel. What a nightmare. Maybe with a mill you could get all of the holes to align, but not a drill press.

Ken