I did build a lock for the gate as follows. First made lock arms from some .060 brass. cut two pieces of 1/8" dia. drill rod and silver soldered on the arms. Cut a piece of 1/4" drill rod and drilled and taped 8-32 right the way through. Made up and silver soldered on a brass arm to link up to the servo.
Threaded the 1/8" drill rod 10-32 thread and installed it with lock nuts to keep the arm parallel and from turning
Mounted small servo from Helli to the box hooked up the linkage and it worked.
Last photo is the down stop switch for the screw drive. It has a diode bridge on it so it will reverse to go back up.
Thanks for looking
Rob