Downward stairway

From DwarfFortressWiki

This will carve a down stair into a floor, and mine out a wall too if designated there. If no floor is present it can be built using the build interface (bCd).

[edit] Carving down stairs

1. Press d to open the designate menu.
2. Press j to select "Downward Stairway".
3. Move the cursor to a position on or near a wall and press Enter.
4. The spot you marked blinks + indicating where the area you wish to start carving stairs.
5. Move the cursor to any position across the area you wish to carve down stairs and then press Enter again. This area must be a non-built wall. Any area of floor or construction will not be selected. Usually, this is just a single tile.
6. The wall tiles in the area you defined should blink similar to mining.
7. Wait for a dwarf to do the job. You will need to designate/build an up stair or up/down stair for each downward stairway on the z-level below.