Midrash on Numbers 3:36: Bereshit Rabbah & Classical Sources

וּפְקֻדַּ֣ת מִשְׁמֶרֶת֮ בְּנֵ֣י מְרָרִי֒ קַרְשֵׁי֙ הַמִּשְׁכָּ֔ן וּבְרִיחָ֖יו וְעַמֻּדָ֣יו וַאֲדָנָ֑יו וְכָל־כֵּלָ֔יו וְכֹ֖ל עֲבֹדָתֽוֹ׃

the appointed charge of the sons of Merari being the boards of the tabernacle, and the bars thereof, and the pillars thereof, and the sockets thereof, and all the instruments thereof, and all that pertaineth to the service thereof;