The essence of the Sh’china was originally manifest in the physical world. Sins, however, caused it to depart. Then tzaddikim, through the avoda of iskafia, drew the Sh’china back to the world, being especially revealed in the Mishkan and later in the Beis HaMikdash. The Mishkan was made of atzei shittim, symbolizing the avoda of transforming the shtus that permits evil behavior into something holy, shtus d’k’dusha. “Shtus” comes from “shita – inclined,” an inclination, a deviation, towards foolishness. Where extra caution is needed to avoid shtus d’l’umas zeh, shtus d’k’dusha, a “deviation” towards holiness, is required, the effect of which is bringing the Sh’china back to be revealed in the world.