Antonyms for the phrase "puts under lock and key" include "releases," "frees," "unlocks," "opens," or " exposes." These antonyms indicate the removal of any restrictions or confinement, allowing freedom and accessibility. Instead of putting things under lock and key, one may "display" or "showcase" their possessions. Alternatively, instead of locking someone up, one can "embrace" or "welcome" them. These antonyms reflect a more positive and open attitude towards possessions or people, indicating a sense of trust and mutual respect.