The Salon des Independents

When Fountain was rejected by the Salon des Independents, the jury claimed that it was because the artist had not manufactured/made the work themselves. In his defense of the work, Marcel Duchamp claimed that this made no difference. Instead, he argued that it was a work of art because the artist had chosen the object and reframed it.
How does Duchamps reframe the urinal--elevating it from everyday object to work of art?