Another theme exhibited in this hall is autosacrifice, a ritual that was conducted in private as a personal act of communication with the gods. Widespread throughout the entire population, this practice was performed by perforating certain fleshy parts of the body—such as the earlobes, lips, tongue, chest, calves, et cetera—with obsidian blades, agave needles or bone perforators. Once the implement was covered with blood, it was inserted in straw balls called Zacatapayoli. The entirety was probably placed in ceremonial boxes—tepetlacalli—as an offering to the gods. Objects associated with human sacrifice are the "face blades" or knives decorated with eyes and teeth, as well as skull masks. Other ceremonial items include musical instruments, jewelry, and braziers for the burning of copal.