Matthew Poole and continuators on Exodus 27:4

4 And thou shalt make for it a grate of network of brass, and upon the net shalt thou make four brazen rings in the four corners thereof.

Which was competently strong and thick, this being as it were the hearth of the Altar upon which they laid both the wood and the sacrifices, and it was full of holes, through which the blood and ashes might fall down into the place appointed for them.

Or rather at or beside, or under, the net, for so the rings were placed, as their use shews, and the Hebrew preposition, al, is oft so used.

Which were either 1. peculiar to the grate, which by these was carried apart from the Altar, having the perpetual fire kept in it: for had it been carried with the Altar, the cloth wherewith the Altar was covered Numb. 4. 13. would have been endangered by the fire. Or 2. common to the Altar, to which these were fixed on the outside, as on the inside to the grate, that by them the grate might be both kept even and upright, and also carried together with the Altar, and that with such caution that the fire included might not hurt the covering-cloth, which was not difficult to do.