My easiest solution, although admittedly inelegant, is a nice big spring clamp. I've used two of these on our 10x12 doors for years (one up high, one lower.) The benefit to me is they compress the weather seal I added to the gap, and it provides a nice air tight seal the whole length of the doors (a benefit when heating in winter.)

To open the doors I remove the clamp and then re-clip it to one side. Just takes a second. Only complaint is the clamps are so strong it's easiest to squeeze with two hands, which means I have to set my coffee cup down. :-)

Smart cat!