'Keepers' in the Bible

This is the thing which ye shall do: a third part of you that come in on the sabbath, of the priests and of the Levites, shall be keepers of the doors;

He built towers in the wilderness, and dug out many cisterns, for he had much livestock; in the lowland also, and in the plain: [and he had] farmers and vineyard keepers in the mountains and in the fruitful fields; for he loved farming.

And they came to Hilkiah the high priest, and delivered the money that was brought into the house of God, which the Levites, the keepers of the threshold, had gathered of the hand of Manasseh and Ephraim, and of all the remnant of Israel, and of all Judah and Benjamin, and of the inhabitants of Jerusalem.

And the singers, sons of Asaph, are on their station, according to the command of David, and Asaph, and Heman, and Jeduthun seer of the king, and the gate keepers are at gate and gate; it is not for them to turn aside from off their service, for their brethren the Levites have prepared for them.