As he entered the Salon Carré, the thief headed straight for the Mona Lisa. Lifting down the painting and carrying it into an enclosed stairwell nearby was no easy job. The painting itself weighs approximately 18 pounds, since Leonardo painted it not on canvas but on three slabs of wood, a fairly common practice during the Renaissance. A few months earlier, the museum’s directors had taken steps to physically protect the Mona Lisa by reinforcing it with a massive wooden brace and placing it inside a glass-fronted box, adding 150 pounds to its weight. The decorative Renaissance frame brought the total to nearly 200 pounds. However, only four sturdy hooks held it there, no more securely than if it had been hung in the house of a bourgeois Parisian. Museum officials would later explain that the paintings were fastened to the wall in this way to make it easy for guards to remove them in case of fire.