Introduction: Mailbox Delivery Indicator Flag

The USPS (United States Postal Service) offers Informed Delivery emails when the patron is receiving mail. This a good thing, as it lets you know that you're getting mail that day. However, only letter size envelopes and cards are scanned and listed; news papers, manilla envelopes, fliers, etc. are not scanned. So, one might think that they weren't getting mail that day, not check it, actually have important paperwork there, and have it ruined by rain, or have it stolen. We've all made trips to the mailbox to check for mail, in all kinds of weather, only to come back empty-handed. It's frustrating. I wanted a thrifty solution that would would tell us if the mailbox had been opened (by anyone) or not. Hence, this cool little indicator flag. Even with all new parts (some I already had), this project should cost near, or even under, $10. Not bad! In my version, I used an American flag; use what you wish. Door stays closed, flag stays down, door is opened, and Old Glory flies in the breeze. Patriotic and practical, all rolled in to one! Want to save a few steps (and a few bucks)? Give this a try, you'll be glad you did. :)

Step 1: Parts List and Required Tools.

1 - 2" corner bracket - Lowes Item # 809448

1 - 1/4" x 12" aluminum rod (available at hardware stores or Tractor Supply)

1 - spring door stop - Menards SKU: 4318264

1 - mending brace - Menards SKU: 2256151

4 - machine screws (I used what I had, 1/4" x 1" recommended)

8 - flat washers

4 - nuts with lock washers OR 4 nylock nuts

1 - wire nut (big enough to thread a few turns onto the aluminum rod)

1 - 6" x 4" flag - Party City SKU: 248607

Electrical tape.


Appropriate screw driver for the screws you choose to use.

Wrench, or pliers.

Hand drill with bit appropriate for the size of screws used.

Extension cord if needed.

Measuring tape.

Marking pen, or pencil

Step 2: Assembly.

If not already 12", cut the aluminum rod with with a hacksaw, Dremel tool, etc. to the desired length. Next, separate the spring part of the door stop from it's base (it literally threads on to the base), and remove the supplied wood screw (throw it into your screw box or coffee can to save it for a rainy day!). The corner bracket has two holes in each side. Using a machine screw, flat washers and nylock nuts (or regular and lock washers), mount the door stop base, flat side up, with the appropriate screw driver, to the corner bracket using the inside hole.

The spring portion has a rubber cap on top. Puncture it with an awl, screw, or other sharp object, then push the aluminum rod through the hole, most of the way through. Next, wrap the bottom of the rod with electrical tape, to prevent the rod from being thrown out of the spring when it snaps upright. Push the rod up inside the spring until it stops. The flag I used had a very cheap (the whole thing cost 79 cents) plastic mast, that snapped when I tried to push it through the rubber spring cap, hence, the aluminum rod mast, so remove it from the plastic one,. Thread the flag onto the aluminum rod from the top. Wrap a couple turns of electrical tape on the rod below the flag to hold it in place. Then thread the wire nut on to the top of the rod. Wrap the rubber cap, and about 1" of the top of the spring with electrical tape to make sure the rod stays put. Screw the spring portion back on to the base, and the indicator flag is ready to install.

Step 3: Installation.

You can install this however you wish, but I installed mine to be visible above the mailbox by a fair amount. Use your own discretion. Here's how we did it.

On the lid of the mailbox, place the mending brace up 5 1/2" up from the bottom left corner of the lid itself. Drill a hole into the lid through one of the slots in the brace. Using a machine screw, nut and washers, mount the brace to the lid. Then, measure back 10 1/2" from the lid toward the rear of the box, and up 4 1/2" from the bottom of the mailbox and make a reference mark. This where the bottom of the corner bracket will be at. Placing the bracket at the reference mark. drill two holes through the holes in the bracket into the mailbox. Using machine screws, nuts and washers, install the corner bracket to the mailbox. Screw the finished flag back onto it's base on the bracket, then holding the bottom of the spring, SLOWLY bend the spring over and hook the flag rod underneath the brace on the lid. The first time you bend the spring over, it will be stiff from the paint on it; the turns will be "glued together" by the paint. This breaks easily, and allows the spring to fully flex. Open the lid of the mailbox; the flag rod should slide smoothly under the brace/latch to the end: the flag will snap into the upright position, and presto! You will now know when the mailbox has been opened. No more wondering if you have mail, or wasted trips in the rain! Enjoy.