As soon as the last ballot drops, all those signs in your front yard are trash. The ones on the side of the road? Trash.

Corrugated plastic, usually made from polypropylene, is not recycled by the Spokane Regional Waste System. This election season’s challenge: reuse the flexible, light and durable material. Use it for bike accessories like fenders, panniers or a tool bag. Make an inbox and outbox for your desk at work. Build a cage for your hedgehog or a case for your ukulele. Use it for things nobody’s used ever thought of. We dare you.

TERRY SAWYER’S “BIPARTISAN” KAYAK

We dare you to one-up Gonzaga University Law Professor Terry Sawyer, who is in the final stages of building a super light-weight kayak from campaign signs.

Sawyer chose corrugated plastic, best known as coroplast, because it’s light — he can lift the kayak with one arm. Honorable mention goes to the fact that you can find it for free. Sawyer gathered his coroplast stash from the side of the road after last year’s election and has so far spent under $50 on the project.

He used instructions from a book on building a kayak from plywood, modifying them to accommodate for coroplast’s idiosyncrasies. It doesn’t adhere with most glues, so he’s been using “good ole’ contact cement” for parts that need flexibility and hot glue for non-moving parts. He sealed up edges using duct tape and fastened corners using zip ties. Coroplast is less structured than plywood, so he hot-glued in a frame built with PVC piping.

The corrugated ribbing makes coroplast flexible, says Sawyer, so when you’re starting your project, make sure the ribs are horizontal in the direction you need the coroplast to bend.

He took the partially-completed kayak on the lake in August. Both he and the kayak survived the ordeal, although he did tweak a thing or two afterwards. Despite a successful first run, Sawyer isn’t entirely confident about taking the kayak out in deeper water — at least not yet. “My main concern is that it’ll just fail completely and utterly somewhere and I’ll have to swim a pile of junk to shore,” he says.

KENT PETERSON: THE COROPLAST MASTER

There’s a special holiday in the Peterson’s household: Coroplast Harvest Day. It’s the day after elections, when Kent Peterson, shop manager at Bike Works in Seattle, drags the family out to help collect campaign signs.

Even though candidates are responsible for collecting their own signs after elections, says Kent, the city ends up cleaning up much of what’s left out on right-of-ways. In the one instance where a police officer stopped him to ask what he was up to, a simple explanation sufficed.

Peterson suspects he was among the first to make bike fenders out of coroplast 12 years ago. “I had a bike that had kind of weird dimensions and I couldn’t get fenders to fit,” he recalls. He experimented with several materials and found coroplast fenders, affixed to the bike using UV-resistant zip-ties, to be most useable.

Now Peterson is kind of a coroplast-fender legend. Years ago, it was such a small cult movement that his friend found a note attached to his coroplast fenders asking, “Do you know Kent Peterson?” But these days, says Peterson, they’re standard issue for trendy young bikers in Seattle’s U-District.

It’s no wonder, either, that the idea caught on. Assuming you’re using an old sign, the project cost is about sixteen cents — the cost of a handful of zip-ties. And unlike Sawyer’s kayak, you don’t need a law degree to figure out how to make them.

“I can probably throw a set of fenders —from ground zero to having somebody fendered in about half an hour,” says Peterson. Find the dimensions for bicycle-accessory projects by holding the sheet up to your bike.

He has now taken the coroplast thing to new levels, making panniers and every other size and shape of storage box for bikes. A particularly fun project, he says, is building a custom-shaped box to fit in the main triangle of the bike, perfect for carrying a pump, patch kit and tools. People who attended a workshop he gave last year made all kinds of things, some unrelated to bicycling — coroplast is perfect for building any lightweight, boxy thing you can think of, he says.

For non-campaign-season coroplast projects — particularly smaller ones — Peterson suggests asking a local sign shop for their scraps. For more involved projects, like model airplanes, you may need to hunt down a thinner version of coroplast than the one used for campaign signs.

“I’ve been joking with my wife that we could make an entire house out of it,” he says, “but she totally draws the line there.”