וַחֲמֵ֨שׁ עֶשְׂרֵ֥ה אַמָּ֛ה קְלָעִ֖ים לַכָּתֵ֑ף עַמֻּדֵיהֶ֣ם שְׁלֹשָׁ֔ה וְאַדְנֵיהֶ֖ם שְׁלֹשָֽׁה׃
The hangings for the one side [of the gate] shall be fifteen cubits: their pillars three, and their sockets three.
Read kabbalistic (mystical) interpretation of Exodus 27:14: and classical mystical sources.