We need a screen on the main door. I was going to hang a dangling screen thing like you can buy for your home doors and cut it down to size, but I didn't really care for that idea.
I want a real door, one that you can open and shut and not have issues with, so that's what I came up with.
The door had to be removable because it sits in the same track that the regular door closes into, and shares the same weather stripping for a sealing surface. So I bought a 25 pack of rare earth magnets on Amazon with the plan of recessing some in the hinge side of the door, and a matching set in the door jamb so that I would simply put the screen door unit in the hole, and the magnets would catch each other and hold everything in place until I pulled the door back off.
Like this:

I built a lightweight door frame out of 3/4" thick cypress and made the stiles and rails 1" wide. I reinforced the corners with blocks and glued and shot everything together.


Epoxying the magnets in door side:

Test fit once epoxy dried and both sets of magnets installed:

All I do is set it in the hole, and the magnets self align and snap the door in place. I used 9 magnets per side.
Screened and painted black:

