Cat Doors

We have three back doors; the entry door, the kitchen back door, and the woodshed door. Only the woodshed door opens out, into , yep, the woodshed. 
We have a relatively strict rule about Cats After Dark, since we live in the middle of the woods, and there are a lot of things that eat other things, including cats.  When I get up in the morning in the fall and spring, it's pretty dark out there at 5 and 6 am.  This morning I was up at 6, made my coffee, explained 18 times to a very impatient Charlie that no we do NOT let you out until I can see the sky lighting up. 
I"ve never seen him this frantic, lol.  He tried the cellar door, jiggle jiggle, he tried the other two out- side door handles, jiggle jiggle, and then the woodshed door. JIGGLE JIGGLE clank clank and I looked over to see him hanging off the latch with one paw and wiggling the lifter with the other.  And then the door made a squeak, and out he went.

We've never bothered with a hook on it, because it's really an inside door and the shed is locked when we leave. 

However, apparently a 13 lb determined cat can muscle it open just fine.  There may be a hook and eye in his future, if he does it again.