Scroll Rack is a way to exchange a known hand for the unknown top of your library. Pay one mana and tap it, exile any number of cards from your hand face down, then take that many cards from the top. The exiled cards go back on top in the order you choose. Your hand size normally stays the same; the advantage comes from selection and control over future draws.
Land Tax provides a classic partnership. The lands it finds can become cards you exchange through the Rack, and a later library shuffle can move the returned cards away from the top. Fetch lands offer a similar shuffle opportunity when you no longer want to draw the cards you placed there.
You can also arrange specific reveals. A card placed on top may support a miracle spell on a later draw, a commander that uses the top of the library, or an upkeep reveal such as Twilight Prophet. That use treats the returned cards as deliberate setup rather than unwanted leftovers.
The exchange is not drawing cards, so effects that trigger from draws do not apply to the cards entering your hand this way. It also does not create additional cards by itself. Without a shuffle or another way to use the arranged top cards, you may simply encounter the same cards again. Scroll Rack rewards a deck that can manipulate the library around it, turning the top-card information and hand exchange into a repeatable plan rather than an occasional attempt to escape a weak hand.






