This!

You might recall I had been trying to figure out a way to hold the Rolling Steel Tent's rear door partly open in a way that the wind couldn't blow it open or closed. You might also recall that Forrest came up with a very simple solution. A block, a bungee cord, presto.

I was happy with that solution until I saw what Swankie uses. It's called the Ventlock.

It comes in several lengths, depending on how far open you want to hold your door or hatch. I'd like to show the video demo here, but they've disabled embedding so here's a link to it.

The hook screws out of the heavy steel rod. You slip the hook over the loop or post part of your door/hatch lock system (see samples below) and spin the rod to tighten.

When that's done, the rod won't come off the loop or post. Then you poke the looped end of the rod into your latch mechanism—the part that would ordinarily click over the loop/post on the door frame. Then you just reverse the process to remove the Ventlock. If you have powered remote locks, then your door/hatch is secure. But if you just have manual locks (like me), someone could reach in an unlock the door. So Ventlock isn't a security device in those instances.

Unfortunately, they're not cheap. But someone with some basic welding skills could make one. Or if you don't need or can't use the security aspect, then a clip at one end of a stick and a loop on the other will work just as well. I think I need to make a trip to the hardware store.