Shekalim, Chapter 5, Mishnah 2. Our Mishnah continues to discuss the various positions and offices that existed in the Beis Hamikdash.
"Ein pochasin mi'shloshah gizbarin":
There were never fewer than three treasurers in the Beis Hamikdash. They were responsible for the redemption of items that people had consecrated, and in general all monetary matters of the Beis Hamikdash were conducted according to their word.
"U'mi'shivah amarkolin":
There were never fewer than seven amarkolin. They held the seven keys to the gates of the Courtyard, and anyone who wished to open the gates had to gather all seven of them together for the opening. Interestingly, the Beraisa explains that they were called amarkolin from the expression "amir ela kol" - "amir" in Arabic means a prince or the like, and they were the appointed officers; so the word is connected to that Arabic word.
The Katolikin and the order of the hierarchy:
The Mishnah teaches that above the amarkolin there were also two officers called katolikin. It appears that the name is related to the general word catholic, which does not mean the Catholic religion but rather denotes something all-encompassing and universal, because their responsibility was broader. The Rambam explains that there were five levels of hierarchy in the Beis Hamikdash:
The Kohen Gadol - at the top.
The Segan - his deputy.
The two katolikin.
The seven amarkolin.
The three treasurers.
"V'ein osin serarah al ha'tzibbur b'mamon pachos mi'shnayim":
No official position or office that has authority over the public in monetary matters is filled by fewer than two people. Out of respect for the public, every position that carries authority over the public in financial matters must involve at least two people.
The Mishnah lists only two exceptions:
"Chutz mi'Ben Achiyah she'al cholei me'ayim" - Ben Achiyah, whom we mentioned was the officer in charge of treating intestinal ailments in the Beis Hamikdash.
"V'Elazar she'al ha'parochos" - Elazar, who was the officer in charge of the curtains.
"She'osan kiblu rov ha'tzibbur aleihem" - the majority of the community accepted both of them upon themselves as individuals. Even though they presumably needed to raise money for these purposes, and even though this involved collecting money from the public, they were permitted to do so as individuals, since the public had accepted them as those officers.
In summary: In this Mishnah we learned the numbers of officers in the Beis Hamikdash - three treasurers for matters of money and redemption, seven amarkolin who held the keys to the gates of the Courtyard, and two katolikin above them - as well as the five levels of hierarchy listed by the Rambam, from the Kohen Gadol down to the treasurers. We also learned the rule that no position of authority over the public in monetary matters is filled by fewer than two people, out of respect for the public, and the two exceptions - Ben Achiyah who was in charge of intestinal ailments and Elazar who was in charge of the curtains - who were permitted to serve alone because the majority of the public had accepted them upon themselves.