וְעָשִׂ֥יתָ אֶת־הַקְּרָשִׁ֖ים לַמִּשְׁכָּ֑ן עֶשְׂרִ֣ים קֶ֔רֶשׁ לִפְאַ֖ת נֶ֥גְבָּה תֵימָֽנָה׃
And thou shalt make the boards for the tabernacle, twenty boards for the south side southward:
Read kabbalistic (mystical) interpretation of Exodus 26:18: and classical mystical sources.