The four corners that are on the four feet, is scarcely an intelligible expression. Pe'oth, the word translated "corners," means properly "ends;" and the direction seems to be, that the four rings should be affixed to the four "ends" of the table; those ends, namely, which are "at the four feet."
It is a periphrasis, meaning no more than that they should be affixed to the feet, as Josephus tells us that they were. (Ant. Jud. 3.6, § 6.