Our newly set up mailbox needs a sign indicating outgoing mail. Since the mailbox is made of plastic, we don't want to fix any additional items on the brand-new brick structure.

Later, I found a set of magnets here:

https://www.amazon.com/gp/product/B01M6B86Y3/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

First, I designed a magnet base

If you print the flagpole

Due to the large size of the hinge and my desire to clearly show the layered effect, I chose to place it horizontally on the print raft for printing.

On the inside of the mailbox lid, I used black electrical tape to fix a flat steel plate to the inner wall of the lid.

When there are no emails to be sent in the mailbox, we will store the magnet on the inside of the lid, as shown in the figure.