I used two jigs for frame construction, one simple for chainstays and one for final assembly.
The jigs were made from wood slabs according to building plans. The purpose of these jigs was to hold all components of the frame (dropouts, BB shell, head tube ,seat tube) on the precise place during assembly. All units are in millimeters.
Chainstay construction jig
The first jig secures fixation of rear dropouts to chainstays and all this construct to BB shell. BB shell and dropouts are in perfect vertical alignment.
Final construction jig
I used the first jig for construction of the final jig. Stops holding the BB shell on place were moved so that prepared chain stays were moved up to rear vertical part of the jig. The fork and BB shell axle lay on the same horizontal level.
I used the old bike frame as a dimension template according to it I constructed the jig itself. Angle of the saddle tube was not changed. I fixed this tube using the wooden rod that was put between two wooden slabs of the top part of jig. Fork was localized by thinner wooden rod, the angle I decreased for about half of degree.