A Romulan puzzle box with sliding panels that opens only with patience, used as a toy and thinking aid by the Tal Shiar agent Narek.
The tan zhekran is a small cube whose faces must be turned and slid in the right order before it will open to release whatever is kept inside. Romulans regard it as an exercise in patience.
It appears in the first season of Star Trek: Picard, chiefly in The Impossible Box. Narek fidgets with his box while considering how to draw out the hidden memories of Soji Asha, and his sister Narissa, who never had the patience for it as a child, mocks his slow methods.
Once he has what he needs, Narek leaves the box in a sealed room with Soji and lets it open to release a lethal radiation, a murder attempt she survives only by her android abilities awakening. A similar box holds a Romulan scientist's diary in Discovery's fifth season.