Replaces the stock flag for when the mailbox door opens.

You can go to the free OnShape link if you want to modify the model.

OnShape:  https://cad.onshape.com/documents/e2505c475234edceecdd81c4/w/df53b840196bc3486d583b40/e/bb1dd8e7a72564817ecf8358?renderMode=0&uiState=65be9ebc430e5650ecd43ace

Mailbox:   https://www.amazon.com/gp/product/B01KJEFJ4I/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1