Easiest and Cheapest Car Signs for Ad, Celebration, or Protest

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If you want to advertise your business or are in a car caravan celebration or protest, you may consider buying car stickers, car decals, or car magnets, but a lot of times these events are one-time events — you may not want the signs afterward, and you don’t want to damage your car. So here are the easiest and cheapest ways to put up your signs.

This DIY idea is very quick, simple, cheap, causes no damage to your car and there is no clean up afterwards. Just recycle your cardboard and reuse your shoelaces!

Also, although it may seem quite unrelated, this same technique used for hanging signs can be employed in the winter to reduce overnight ice buildup on your windshield, so check out our other video which discusses that topic: https://youtu.be/Sv-UbOkAy_U

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For the full video tutorial, visit Genius Asian.

The Cardboard and Shoelace Method in Detail

The core idea is brilliantly simple: use a piece of cardboard as your sign face, thread shoelaces or string through holes punched in the cardboard, and hang the sign from your car window by closing the window on the laces. The window clamps the laces in place, the sign hangs flat against the door, and when you are done you just open the window and pull the laces out. Zero adhesive, zero damage, zero cleanup.

Materials You Need

Cardboard: A flat piece from any shipping box. Cut it to the size you want — 12 x 18 inches is a good all-purpose size for car door signs. Double up the cardboard (two layers glued together) for rigidity if it is windy.
Shoelaces or paracord: Two laces per sign. Standard 36-inch flat shoelaces work perfectly. Paracord (550 cord) is tougher if you plan to drive at highway speed.
Markers or paint: Sharpie Magnum markers are the fastest option for bold, readable text. For larger lettering, use spray paint with a stencil.
Hole punch or awl: Punch two holes near the top edge of the cardboard, about 6 inches apart.

Assembly Steps

Cut your cardboard to size. Keep the fluting (corrugation) running vertically so the sign does not sag.
Write or paint your message. Keep text large — at least 3-inch-tall letters for readability at 30 feet. Use high-contrast colors: black on white, white on red, or yellow on black.
Punch two holes about 1 inch from the top edge. Reinforce the holes with packing tape to prevent tearing.
Thread a shoelace through each hole. Tie a knot on the back side so the lace cannot pull through.
Open your car window about 4 inches. Drape the laces over the top of the window glass so the sign hangs outside. Close the window to clamp the laces.
Adjust the lace length so the sign sits centered on the door panel.

Tip: For highway driving, add a third lace at the bottom of the sign tied to the door handle or side mirror bracket to prevent flapping.

Alternative Methods

1. Magnetic Car Signs

When to use: Repeat use for business advertising or event signage that you put on and take off regularly.

Pros: Clean appearance, repositionable, no adhesive residue, professional look with custom printing
Cons: Cost more than cardboard, can scratch paint if dirt gets between the magnet and the car, do not stick to aluminum or fiberglass body panels
Difficulty: Easy
Estimated cost: ~$15-40 per pair for custom-printed magnetic signs, ~$5-10 for blank magnetic sheets from a craft store

2. Static Cling Window Signs

When to use: Messages that need to face outward through the window glass.

Pros: Completely removable with no residue, visible from inside and outside, reusable, rain-proof since they are behind glass
Cons: Only works on glass surfaces, limited size (must fit your window), sun glare can reduce readability
Difficulty: Easy
Estimated cost: ~$10-25 for custom prints, ~$3-5 for DIY using static cling vinyl sheets from Amazon

3. Window Paint Markers

When to use: Celebration messages like “Just Married,” graduation congratulations, or team spirit.

Pros: Eye-catching and colorful, removable with a razor blade and glass cleaner, available at most craft stores
Cons: Only suitable for windows (not paint), messy to remove if left on too long in sun, smears in rain if not a rain-resistant formula
Difficulty: Easy
Estimated cost: ~$5-12 for a pack of window markers (Uni Posca or Window-Chalk brand)

Tips and Tools

Weather protection: If rain is in the forecast, cover your cardboard sign with clear packing tape on both sides or use a sheet of clear contact paper. This adds a waterproof layer and extends the sign’s life from one event to several.
Double-sided signs: Make two identical signs and hang one on each side of your car for maximum visibility in a parade or caravan.
Nighttime visibility: Attach a strip of reflective tape (3M Scotchlite brand) along the edges of your sign. In headlight beams, the reflective tape makes your message readable at night.
Legal considerations: Check your local traffic laws before driving with signs. Some jurisdictions restrict sign size or placement if they block the driver’s view. Generally, signs on rear side windows are allowed, but signs that obscure the windshield or front side windows are not.
Reusability: Laminate your cardboard sign with wide packing tape for reuse at multiple events. Store flat in your trunk between uses.
For DIY signage with a cleaner look, check out our guide on the quickest way to build things with lessons learned from fence building — many of the same planning and material principles apply to any fast build project.

When to Call a Pro

For most one-time events, the DIY cardboard approach is all you need. But here are cases where spending money on professional signage makes sense:

Business vehicle branding. If you are a contractor, real estate agent, or delivery service, professional vehicle wraps or magnetic signs with your logo, phone number, and license number project credibility. A full vehicle wrap from a shop like FastSigns or a local sign company runs $1,500-3,000 but lasts 5-7 years.
Large fleet signage. When you need consistent branding across multiple vehicles, a professional sign shop ensures color matching, proper sizing, and durable materials rated for highway speeds and car washes.
Permanent commercial lettering. DOT-required truck lettering (USDOT number, company name, GVW) must meet specific size and placement regulations. A sign shop familiar with DOT rules will keep you compliant.

For other creative DIY approaches to everyday problems, check out our guide on making your own DIY face shield in 2 minutes — it is another project where simple materials and clever technique beat expensive commercial options.

Always verify contractor licensing and insurance in your state. Cost estimates are averages and may vary by location.