Sentence:  Some time in 1912 , Picasso cut out and folded a piece of paper in the shape of a guitar ; to this he glued and fitted other pieces of paper and four taut strings , thus creating a sequence of flat surfaces in real and sculptural space to which there clung only the vestige of a <WSD>picture</WSD> plane . 
Meaning of the word marked with <WSD> tags:  the plane that is in the foreground of a drawing or painting; coextensive with but different from the objective surface of the work