וַיִּצֹ֣ק ל֔וֹ אַרְבַּ֖ע טַבְּעֹ֣ת זָהָ֑ב וַיִּתֵּן֙ אֶת־הַטַּבָּעֹ֔ת עַ֚ל אַרְבַּ֣ע הַפֵּאֹ֔ת אֲשֶׁ֖ר לְאַרְבַּ֥ע רַגְלָֽיו׃
And he cast for it four rings of gold, and put the rings in the four corners that were on the four feet thereof.
Read kabbalistic (mystical) interpretation of Exodus 37:13: and classical mystical sources.