Top-Down / Bottom-Up (TDBU)

Top-down/bottom-up lets a shade open from the top as well as the bottom, so you can drop the top edge to let daylight in over a privacy screen that stays up from the sill. It’s the neatest answer to the street-level window problem — light without exposing the room — and it’s most common on cellular shades because their light, stackable fabric suits the dual rail. The trade-offs are a slightly bulkier headrail, a modest price premium, and two rails to operate. Where privacy and daylight both matter (bathrooms, ground-floor bedrooms), TDBU earns its keep more than almost any other option.