Fred and George Weasley show Harry the Marauder's Map that they stole from Filch's office. The map shows all of Hogwarts and the movements of every person on the premises in real-time. The map also shows all of the secret passageways around Hogwarts.
Charlie helps Don find a missing painting by creating a diffusion map. Using an example of a truck, Charlie explains how travel options and routes are limited depending on what a person is transporting.