We created this outdoor pergola with a shed roof using cedar and corrugated metal to protect the cook from rain while barbecuing. The whole back-garden design has the feel of being at the ranch.  I think they need one of those metal triangles to call us all to dinner!

Corrugated galvanized iron (CGI) is very useful building material composed of sheets of galvanized mild steel that is then rolled to produce a linear corrugated pattern. It was invented by the British architect and engineer Henry Palmer in 1820. Originally it was made of wrought iron but now we use steel. The corrugations pattern aides in the bending strength of the metal sheets in a perpendicular direction to the corrugations. It is a strong, light weight, rust resistant material that is easy to transport. It has been used as a favored building material in Australia since 1840.

Uniformity of the pitch and depth of each sheet is an important aspect of its manufacturing. This consistency makes the sheets stack-able for transporting. Pitches have ranged from 1 to 5 inches with the shorter pitches used for walls and was called rippled instead of corrugated. Now you will commonly find only the 3inch pitch. It is this consistency in the corrugation that makes it easy to use as a fence, wall or roof construction material. Overlapping the sheets creates a waterproof surface.

CGI is most commonly used commercially applications but can also be found around the world for residential uses especially in developing countries. The galvanizing process does help protect against rust and corrosion but doesn’t prevent it. Painting the CGI can protect the metal even longer.

Fun fact: Clapping hands or snapping ones fingers whilst standing next to perpendicular sheets of corrugated iron (for example, in a fence) will produce a high-pitched echo with a rapidly falling pitch. This is due to a sequence of echoes from adjacent corrugations.
All the information in this post was gleaned from – https://en.wikipedia.org/wiki/Corrugated_galvanised_iron