How to make a face go straight down?

Hi!

How can I make a face go straight down like in the first picture and not like in the second picture? And please tell me the hotkey to it :wink: (e.g Ctrl+S (save)) If you understood what I mean by this (You probably don’t) please answer :smiley:
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untitled.blend (472 KB)

Extrude, shortcut E

The face will extrude along the face normal but you could press an axis key (X, Y or Z) to constrain along that axis