Final answer:
The significance of the use of oil putty and plates in Julian Schnabel's art lies in the extension of Cubist practices, symbolizing the breaking of traditional boundaries and the investigation of form, space, and the physicality of materials.
Step-by-step explanation:
The use of oil putty and plates in Julian Schnabel's painting "What to Do With a Corner in Madrid" signifies a continuation and transformation of Cubist ideas and techniques that were originally innovated by artists like Pablo Picasso and Georges Braque. This approach exemplifies how traditional methods of creating art were challenged and reinvented during the early 20th century.
Incorporating unconventional materials such as oil putty and various objects directly onto the canvas was akin to the practices of Picasso and Braque who introduced collage and combined industrial elements with fine art, thereby dismantling the boundaries between 'low' commercial culture and 'high' culture. This method emphasizes the physicality of the materials and questions the very nature of artistic representation, space, and form.