Calm and Collected

The Mishnah in Shekalim says there were 13 monetary collection containers in the Beis HaMikdash. There is no Talmud Bavli on Shekalim; therefore, at the end of Menachos, the Gemara elaborates on the reason for the many containers.
The Gemara offers six different reasons for the final six containers. Chizkiyah opines that all six containers served the exact same purpose. Every day in the Beis HaMikdash, people would take the opportunity to offer their personal sacrifices. Some of these sacrifices may have been obligatory, such as to atone for a sin. Others may have been brought because of a vow made in a moment of inspiration. However, when the kohanim finished offering all of those personal sacrifices, the Mizbeiach may have had some downtime. The kohanim would then take money from the six collection containers, called shofros due to their shape, and purchase extra communal sacrifices. These communal sacrifices were not obligatory in any way. It was a way of honoring Hashem, ensuring that the Mizbeiach not have any interruption in use.