Moreover thou shalt make the tabernacle with ten curtains: of fine twined linen, and blue, and purple, and scarlet, with cherubim the work of the skillful workman shalt thou make them.
(Torah, “Exodus,”, “The Tabernacle”, 26:1)
It’s about the way threads should be “inter-twisted,” from left to right or from right to left. It’s also about what material is used to make a basis and which one is on top of another, linen or wool, and what colors they are. There are natural fabrics like wool, linen, leather of which garments, capes and curtains (canopies) are made.
“Ten curtains” correspond to ten Sefirot and represent a screen that we have to make. On one hand, a screen consists of the egoistic desire; on the other hand, altruistic intention. It implies that a screen should consist of both right and left lines, “wool and linen.”
In ordinary life it is prohibited to join these materials. It is forbidden to wear clothes that are made of both fabrics. However, it is allowed in a place when doing things with a correct and accurate intention that makes the “ratio” between both “fabrics” right, whereas in everyday life it is not apparent if it is so. This explains why one cannot combine the right and the left lines together, an egoistic desire with the altruistic intention, because first one must connect both of them into a middle line.
From KabTV’s “The Secrets of the Eternal Book” 8/12/13