You say "Coroplast."

I say "Corrugated Plastic." 

 Although these two phrases are often used interchangeably, they are only different by name. Coroplast is the brand name of the most well-known manufacturer of corrugated plastic. Other popular corrugated plastic manufacturers are Correx, Twinplast, and Polyflute. Here at Online Yard Signs we use Coroplast for all our corrugated plastic projects.

Another name for corrugated plastic is corriboard, so these two terms can be used interchangeably without regards to brand recognition. The two main types of corrugated plastics are twin-wall (also known as fluted, shown in image above) and wave-like (shown in image below).

Corrugated plastic is just like cardboard, except it is plastic. Their structures are very similar. Corrugated plastic, though, is mostly made from polypropylene. Since this material resists chemicals, oils, UV light and solvents at normal temperatures, it is ideal to endure outdoor weather.