The latch is a locking pin/rewind pin from a BAK-12 aircraft arresting barrier that the USAF uses. You pull up on the T handle and the two balls in the other end are released and the pin can be pulled. You can find a pin like it at a tractor/farm supply store.




The auto-locking pin is home built. Starting with a ¥ö bolt. I welded a ring on top and drilled a small hole on the side of the shank. The bolt slips in and the spring is held with a cotter pin (on the bottom of the spring) so it is always trying to push the bolt down. As the swing-arm is opened and aligns with the hole in the bumper, the bolt drops down and locks the swing-arm open. Lift up on the bolt and swing the arm when closing.