PERGOLA COVER
A pergola is an outdoor garden feature forming a shaded walkway, passageway, or sitting area of vertical posts or pillars that usually support cross-beams and a sturdy open lattice, often upon which woody vines are trained. The origin of the word is the Late Latin pergula, referring to a projecting eave. As a type of gazebo, it may also be an extension of a building or serve as protection for an open terrace or a link between pavilions. They are different from green tunnels, with a green tunnel being a type of road under a canopy of trees.
Pergolas are sometimes confused with arbours (arbors in American English), and the terms are often used interchangeably. An arbour is generally regarded as a wooden bench seat with a roof, usually enclosed by lattice panels forming a framework for climbing plants. A pergola, on the other hand, is a much larger and more open structure and does not normally include integral seating.
Modern pergolas
Modern pergola design material including wood, vinyl, fiberglass, aluminum and chlorinated polyvinyl chloride (CPVC) rather than brick or stone pillars, are more affordable and are increasing in popularity. Wooden pergolas are either made from a weather-resistant wood, such as western redcedar (Thuja plicata) or, formerly, of coast redwood (Sequoia sempervirens), are painted or stained, or use wood treated with preservatives for outdoor use. For a low maintenance alternative to wood, vinyl, fiberglass, aluminum and CPVC can be used. These materials do not require yearly paint or stain like a wooden pergola and their manufacture can make them even stronger and longer-lasting than a wooden pergola.
Reference:https://en.wiki pedia.org/wiki/ Pergola