key on
verb- To anticipate a play by watching and analyzing the movements of one's opponent(s).
- To instruct or make (someone) aware of (something). · She keyed me on to the plan.
From the library
Now put the key on the inside.
There seemed to be no use in waiting by the little door, so she went back to the table, half hoping she might find another key on it, or at any rate a book of rules for shutting people up like telescopes: this time she found a little bottle on it, (“which certainly was not here before,” said Alice,) and round the neck of the bottle was a paper label, with the words “DRINK ME,” beautifully printed on it in large letters.
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