Reusing Campaign Signs: Making a Mini Bookcase

Why is Corroplast® a fascinating material?

Corroplast® or corrugated plastic sheets have become a ubiquitous part of our lives, often seen used for campaign, graduation, and other yard signs. Despite being made of a thermoplastic, these yard signs are seldom recycled. Like plastic bags, yard signs get caught in single-stream recycling sorting machinery and are not accepted. They require specialty collection and recycling programs. These are fairly rare, so let's get to reusing them!

Besides being easy to find and reuse, corrugated plastic sheets are

1. Easy to cut
2. Lightweight
3. UV resistant
4. Waterproof
5. Very strong when you use its properties.
6. And More!

At the end of the instructable, I have more tips for working with Coroplast®, other instructables, and a YouTube Playlist for more inspiration.

Materials

1. Large Coroplast Sign 48” x 48”
2. 2 Smaller signs 18" x 24"
3. ⅛”x1” cotter pins (~16)
4. Wood for Faceframe and Base
5. Wood Glue

Tools

1. X-Acto or Hobby Knife
2. Ruler or Straight Edge
3. Drill
4. Table Saw

Some tools and materials can be substituted.

The prime time to get free signs is after campaign season. Always research your local laws and regulations around campaign signs. The best thing to do is ask individuals and campaigns for them after the election. Some candidates may wish to reuse their signs for future elections. Asking businesses is also great because they may have larger sheets like the ones I used for this project. Some of the signs I took were improperly installed, abandoned for months, or had become litter.

Corrugated plastic sheets come in many thicknesses but the most common is 4mm.

The sizes you will typically see are:

18” by 24”

12” by 18”

48” by 48”

48” by 96” If you’re lucky. (These are really fun to walk home with on a windy day.)

If you were to buy a new 18” by 24” sign they cost around $5. A full sheet costs ~$40.

Cutting strips

First I cut 3 strips to make the three boxes that would form the bookcase. Although more challenging, here you will want to cut across, or perpendicular to, the flutes. The width that you cut these strips will determine the depth of the bookcase. Also, I recommend measuring things out in standard units rather than counting corrugations, not only for your sanity but also for accuracy.

To help the strips fold into boxes, I cut slits halfway through the board, parallel to the flutes. Because of the folding, the distances between score lines will be measured from the left side of the strip as follows:

[ Shelf Height | Shelf Width | Shelf Height | Shelf Width ]

I made the bottom shelf taller on my bookcase by enlarging the shelf height measurement.

Cutting Tips

It’s best to use a ruler or guide and optionally clamps to hold the guide. The plastic is very easy to cut along the flutes (1-2 passes with a utility blade). If you are cutting and it makes a rhythmic sound like a guiro, then you are cutting across and through the flutes. You should expect to make at least 4 passes with your knife. If you are careful to keep your blade straight up and down and take your time, you will get a very clean cut.

When cutting partially through a board to enable easier folding, use a retractable knife to ensure you don't cut all the way through, or carefully use your finger on the side of the blade (away from the cutting edge!) to keep a constant depth.

If you see yourself cutting a lot of Coroplast®, you may be interested in checking out the Corro Claw™. It’s a product that allows you to cut through or halfway through standard fluted plastic when cutting parallel to the flutes. I’ve never used one, but I’d imagine that someone experienced with a utility knife and straight edge may get a cleaner cut.

From Trip the Fantastics' videos about corrugated plastic, I was introduced to using cotter pins. You can attach pieces flat against each other to make a thicker panel, or make an L- or T-shaped joint with the material by pushing an end of the cotter pin into a flute on each piece. Through experimenting, it seemed like the 1/8x3/4” or ⅛ x 1” cotter pins worked the best. Longer pins should generally give you more holding power, but if the pin is too thin, the long legs will more easily deform and have less holding strength once removed and reinserted. The pins can be quite snug once fully inserted; you may need to pry them out carefully with something pointy like a pen, pencil, screw, or nail and some pliers. When testing, you can also thread a string between the prongs before pushing it in and use that to remove the pins.

I folded and attached the strips to make the boxes. Where each box is attached, there is a 90-degree butt joint and a cotter pin at each connection in the front and back. Then I attached the three boxes atop each other using 4 more pins in the front and back at each connection point.

Cutting the inserts

At this point, the shelves would collapse like a deck of cards if we added weight, so we will use the properties of the flutes to stiffen them up. Cut three more strips (cutting across/through the flutes). They should be equal in width to the height between shelves. Use the depth of the shelves to determine the bend points where the plastic will be flush with the back and front of your boxes. I did not use any adhesive here, as the friction is enough and allows it to be removed.

I was stuck for a while, wondering how to make the front edges of the Coroplast® look nicer and hide the cotter pins. After thinking about covering the edges in tape, some sort of putty, or more Coroplast ™, I decided to use scrap pine from my makerspace. The wooden trim is ¾” thick on the front edge, so I was able to rip a few pieces on the table saw from a short 1x4. To make it attach nonpermanently, I made a “U profile” from the strips so it would fit over the two layers of Coroplast ™. You can shim the groove with tape or paper for a tighter fit if needed. The top piece is just like the rest but with a little cap on the top that hides the side pieces' “U” profile from view. I left the bottom uncapped since it is rarely seen. The long pieces on the left and the side also need a notch to go around each horizontal shelf. At first, as you can see in the images, I cut the notch all the way through the piece. To make the notch invisible from the outside, I used a drill and a rasp to help me make a slot on only the inside of the U-profile.

Removing the "Lip"

With the wood trim added, there is a new issue I had to solve. The inside upper edge of the wood trim added a lip that gets in the way of sliding items off the shelves and can knock the trim off. After much overthinking, I realized the gap was exactly the thickness of the signs, so three pieces could be cut to line the bottom of the three shelves. I cut these to have the flutes running horizontally to alternate the direction relative to the two sheets below, like plywood for strength. These are also friction fit.

Designing the Base

For a long time, this project sat unfinished because I didn’t know how I’d make the base. Fusion 360 was really helpful for me to visualize what could complement the design and be proportional. I crudely modeled the shelves and experimented, eventually choosing a design. Another benefit of modeling the base was that I could export the front profile of the legs and laser-cut a guide/template.

Making the Base

I used a piece of (what I believe is) Douglas fir 2-by material for the legs. I cut two pieces to length, then used my crosscut sled to define the 45-degree angles. Next, I hogged out the rest of the material slowly. Again, having the template was very helpful to confirm I was cutting in the right spot. Once that was done, I cleaned up the cuts with sandpaper.

To provide a solid attachment point and keep the legs aligned with each other, I attached them to a 1/16th inch piece of plywood. I wanted the plywood thin so that it wouldn’t be visible under the faceframe. To keep everything flush, I cut a large dado and inset the plywood into the legs using my crosscut sled again. To cover the plywood on the sides of the bookshelf, I took some scraps and made a rabbet that would accept the 1/16” plywood and glued the pieces to both sides of the plywood.

Attaching the Base

There are multiple ways I could have attached the base, but I chose to simply use hot glue. I applied masking tape before hot gluing to make it less permanent.

If there is a slight rock to the bookcase, you can use the old chairmaking trick of laying down a piece of sandpaper on a flat surface and sliding the bookcase over the sandpaper to remove the wobble.

All of the wood was sprayed twice with a matte clearcoat to keep the natural look but provide some protection against water.

I’ve Experimented With

1. Cutting it with a laser cutter (Only do this if you're sure you know what type of plastic you have. Always err on the side of caution before risking your health and your laser cutter).
2. Cutting it with a table saw. It cuts well but produces a lot of plastic dust bits.
3. Removing ink with isopropyl alcohol and a Scotch-Brite pad.
4. Attaching pieces with zip ties. I used a drill bit, an awl, or an ice pick to create holes.
5. Scoring it in different ways to make it more bendy.
6. Drilling it. I’ve found that spade and Forstner bits create cleaner holes, but regular drill bits work too. Just remember to put a piece of wood behind it before you drill.

I plan to Try

1. More Laser cutting
2. Using a pricking iron for leather to punch holes and stitch pieces together. I’d imagine this would be incredibly strong.
3. 3D-printing connectors/adapters (Thingiverse, Printables, Cults3D) and designing new ones.
4. Finding ways to re-use the metal stands.

I've made an art portfolio by taping two pieces together to protect larger drawings. I'd like to make a case, lamp, and chair or ottoman.

Making With Yard signs YouTube Playlist I Made

Other Instructables with Corroplast®

Festfalia, a Ford Festiva Flip Top Hyper Miler Camper

Haunting Your Hood on a Budget!

8 Ft Wingspan Coroplast RC Piper Cub Flown by 25cc Weed Trimmer

Yard Sign Storage Boxes

Thank you for reading. I hope you are inspired to make your own projects from corrugated yard signs and extend their life!

Reduce, Re-use, Recycle.