Simple mechanism that attaches to your mailbox door with a magnet. When the mailbox door is opened the flag flips down so you can tell that you have mail. After you retrieve the mail and close the door, simply flip the flag back up.

The magnet was purchased at Harbor Freight and is approximately 47 x 22 x 9.5 mm.

Printing

PETG because it is used outside.

I printed the “flag” so the first couple of layers were bright green and then printed the rest in black.