How was the last supper secured during world War 2?

During World War II, "The Last Supper," a mural by Leonardo da vinci, was safeguarded by the monks of the Convent of Santa Maria DELLe Grazie in Milan. In 1943, as bombing raids threatened the city, they covered the mural with sandbags and wooden scaffolding to protect it from damage. Despite the convent sustaining damage during the war, the mural itself survived largely intact, thanks to these protective measures.