שמות, פרק ל״ו, פסוק כ״ה

The physical assembly of the Tabernacle progresses systematically, moving from one section to another to form a complete structure. The construction of the wooden frame continues along the northern side. For this specific area, twenty boards were prepared to create the wall. The mention of this being the second side simply indicates its place in the sequence as the second wall of the building to be put together [ביאור שטיינזלץ].