Magnetic box with screen frame.

thingiverse

I created this box originally as a magnetic deck box but then decided to add a screen frame option. The blue circles show where 3mm magnets should be placed, so if you resize the box, you'll need to adjust the magnet size accordingly. The screen frame has two pieces with interlocking cones (highlighted in orange) that make it easy to align and install or glue a screen. I'm considering remixing it with magnets on the bottom, but I'm also leaving that up to individual users to modify as needed.