Rashi citing Beraisa of 49 Midos, Midah 22: They are like tablets, from one Yad Ofan to another. Yad Ofan is the axle that is inserted in the hole in the wheel. The Mechonah had four wheels; there were Misgeros on each side [of the Yad], in all four directions. There were four Amos width between [opposite sides]. Above were Seranim, like Nesarim ¹ (planks) opposite (above) the Misgeros.

Radak: They are [Malbim- planks and a frame] to enclose the laver inside the Mechonah.

Gra: They were sticks, one on another. They made a square four Amos by four Amos.

Rashi citing Beraisa of 49 Midos, Midah 22: They are steps from the lower (Misgeros) to the upper (planks)

Rashi himself, and Targum Yonasan: They are like rungs ¹ of a ladder; copper sticks erected on the lower Misgeros, like two and three between one stick and another. The Misgeros are fixed between rungs. And so Yonason translates 'Shelivaya.'

Gra: They are like legs. The verse does not say how many there were, but it seems that there were three ² , like the oxen under the Yam. They were connected via planks under the Misgeros. The legs were slightly away from the corners of the Misgeros, to allow room for the handles under the wheels.

Malbim: They are interwoven sticks, like a net.

Rashi citing Beraisa of 49 Midos, Midah 22: These are like tablets between the steps, like legs of beds of villagers that are not round, rather, flattened (rectangular), to illustrate on then lions and Keruvim.

Gra: They were sticks, one on another. They made a square four Amos by four Amos.

Malbim: They are thick tablets between the Shelabim and around them, to which the Shelabim were attached.