A sign in your rear window or on the side of your car turns every drive into an ad. Keep it short, big and legal to drive with.
What works on a car
The simplest lost pet car sign is a sheet of poster board or two taped sheets of paper in a rear side window, with LOST DOG and your phone number in thick black marker. It works because people see it at traffic lights and in parking lots. Keep it to two lines and about ten digits. Do not block your view while driving: leave your rear window and side mirrors clear, or use a side window behind the driver. A magnetic sign or window paint is a stronger option if your search runs for weeks.
Choose where on the car
Back side windows are often the easiest spot. People behind or beside you at a light can read them, and the sign is less likely to block your view. Rear windows reach the most drivers, but they can block your rear view, and state rules on what can cover a windshield or a rear window vary. Check your own state’s rules if you want to use the rear window, and never cover the windshield or front side windows. Put the sign inside the car rather than taping it to the outside, so that it does not blow off and create a hazard.
What to write
Your first line should be LOST DOG or LOST CAT. The second line should be your phone number. If there is room, add one word about the color. A driver behind you has no more than a few seconds, and a word like REWARD or a pet’s name adds little at that distance. Use thick black letters on white. Write the phone number with spaces or hyphens between groups so it reads easily. Practice on a scrap first so you do not run out of room before the last digit, which is an easy thing to do.
Materials that work
White poster board and a wide black permanent marker cost little and are sold in most grocery and drugstores. Cut the board so it fits the window. Tape it from the inside with painter’s tape, so it comes off cleanly. Window markers made for cars, of the sort used for school spirit messages, write directly on glass, and they clean off. They can be easier to read when the light is right, but contrast suffers against dark tint, so test them. For a longer search, a sign shop can make a pair of magnetic door signs, which you can remove when you park at home.
Add a photo only if it is big
A photo on a car sign helps only when someone is close, such as in a parking lot. If you add one, put it on the inside of the back side window at the height of a person standing beside the car, and use a full-page color print. A rear-window sign is better left with words only. If your poster is already printed, you can tape one in a side window for free. It adds a useful message for those walking past when your car is parked at a store.
Park to be seen
A parked car can do as much work as a moving one. Leave your car in a spot near the road when you go into shops. Park at the edge of a lot where drivers go by. If a friend offers to help, ask if they would drive around with a sign for a week. Two or three cars taking their ordinary routes through the same area will reach more people than one person doing laps around the block.
Stay safe and stay legal
Do not drive slowly to attract attention, and do not write on the sign while driving. Have a passenger watch for your pet if you are looking while you drive, since a driver looking into yards is a real hazard. If someone waves you down, pull in somewhere safe before you talk. You are displaying your phone number to the public, so follow the same rules as for posters: expect a few strange calls, and do not send money or share codes. Our post on lost pet scams has more on this.
Take it down when it is over
Take down the sign as soon as your pet is home, because people will keep calling. If you have used magnets, take them off every so often to dry the surface below and prevent damage to the paint. Clean any window marker away promptly, because it is harder to remove after weeks in the sun. If you have used tape, peel it off slowly. Keep the poster board in the garage, in case a neighbor ever needs it.