Solution: Feature of a safe landing, perhaps - NYT Crossword

This stacked pair of small entries took me forever to solve. 9A, [“Like, duh!”], solves to OBVS here, short for “obviously,” obviously (well, obviously after filling in the letters, I’d say). OBVS has been in the Times puzzle once before, while “obvi” has appeared five times. What should OBVS sound like, when spoken: “ob – vee – s” or “ahbvz?” I think “obvi” sounds cute, but confess to not using either term. At 21A, [Feature of a safe landing, perhaps], I didn’t think of the area at the top or bottom of a staircase, but they are always safer with a guard RAIL.