Step 6: The latch
The latch is made of scrap plywood about 4" wide. I've got 2 bars that pivot on screws and are kept tight by rails. Another scrap of ply was used to sync the two bars together. I installed carabiners in line with the cables in case I want to lock any one out while I'm on the inside. The door is pretty secure when locked and takes a good shove to get it to move at all.