QUESTIONS ON RASHI
Rashi writes that Ohel Mo'ed are the curtains of goats' hair, and Michsehu is of rams' skin. The opinion that the top cover was half of rams' skin, and half of Tachash, how can he explain? The verse explicitly mentions also "Michseh ha'Tachash"!
Moshav Zekeinim: When they traveled, it was rolled to the middle. From one side, only the rams' skin was seen, and from the other side, only the Tachash was seen, therefore it is considered two covers.