The definition of a leaning pergola is a structure with an open roof that is supported by columns or posts on one side and is connected to a building on the other side of the structure. A leaning patio pergola may be used to extend the inside living area to an outside living area.  This structure can be covered with glass, shade sails or with a professional patio awning.  Pro shade will make sure that besides shade it also adds a designer feature to your house.