שמות, פרק כ״ו, פסוק ח׳

The protective roof of the Tabernacle was designed as a carefully measured system of layers. A set of outer goat-hair curtains functioned as a durable tent, draped over the more magnificent inner layer to provide exact coverage and shelter for the structure.

These outer panels were designed to be thirty cubits long, making them exactly two cubits longer than the inner panels [רש״י, קאסוטו]. Because the flat roof of the Tabernacle spanned ten cubits across, draping these longer curtains over the top left ten cubits of fabric hanging down on each side [תורה תמימה]. The primary approach among commentators is that this extra length was mathematically planned to cover the bottom cubit of the wooden wall boards, which the shorter inner curtains left exposed. Following this calculation, the outer curtains reached perfectly down to the one-cubit-tall silver sockets supporting the walls [רש״י, תורה תמימה].

However, a more precise engineering perspective suggests a slightly different reality in practice. The inner layer was woven from thick, spun threads. When the outer goat-hair curtains were draped over this substantial inner layer, they had to wrap around a wider surface area. Because the thickness of the inner fabric absorbed some of the outer curtain's length, the outer layer could not reach all the way to the silver sockets, inevitably leaving a small portion of the wooden boards exposed near the ground [ביאור יש״ר].

Regardless of how they hung, a uniform size was established for all eleven of these outer curtains. Because eleven is an odd number, when these individual panels were eventually sewn together to form two large covers, the resulting two halves of the tent were necessarily unequal in size [קאסוטו].