Matthew Poole and continuators on Exodus 27:5

5 And thou shalt put it under the compass of the altar beneath, that the net may be even to the midst of the Altar .

(i. e.) Within the square and hollow space of the Altar.

Or, and the net shall be at (the Hebrew, ad, being here used for il, as Hos. 14. 2, Ioel 2. 12. Amos 4. 6, 8.) the midst of the altar. And these words seem added to explain the word, beneath, to shew that as it was not to be at the top, so neither at the bottom of the Altar, but in the midst of it.