Exodus 27:4-8

You shall also make for it a grating, a netting of bronze, and on the netting you shall make four bronze rings at its four corners.

And you shall put it under the ledge of the altar, so that the netting will reach halfway up the altar.

You shall also make carrying poles for the altar, poles of acacia wood and overlay them with bronze.

Its poles shall be inserted into the rings, so that the poles will be on the two sides of the altar when it is carried.

You shall make it hollow with planks; as it was shown to you on the mountain, so they shall make it. Courtyard of the Tabernacle