Manual coop to run door that locks

[nilifer]

The two weird shaped pieces are loose so they can swing out into the niches in the frame to lock the door. And they get swung the other way and pull out of the niches when the middle piece is pulled by the cord.

 

[BigBlueHen53]

I see, thank you. I thought there was a locking mechanism that held it open. I really like this! So can you buy it or is it a DIY?