וְלַכָּתֵף֙ הַשֵּׁנִ֔ית חְמֵ֥שׁ עֶשְׂרֵ֖ה קְלָעִ֑ים עַמֻּדֵיהֶ֣ם שְׁלֹשָׁ֔ה וְאַדְנֵיהֶ֖ם שְׁלֹשָֽׁה׃
And for the other side shall be hangings of fifteen cubits: their pillars three, and their sockets three.
Read midrashic interpretation of Exodus 27:15: and classical rabbinic exegesis.