I Kings 7:28 Midrash

וְזֶ֛ה מַעֲשֵׂ֥ה הַמְּכוֹנָ֖ה מִסְגְּרֹ֣ת לָהֶ֑ם וּמִסְגְּרֹ֖ת בֵּ֥ין הַשְׁלַבִּֽים׃

And the work of the bases was on this manner: they had borders; and there were borders between the stays;