know inside and out

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know inside and out (third-person singular simple present knows inside and out, present participle knowing inside and out, simple past knew inside and out, past participle known inside and out)

1. (transitive, idiomatic) To know (something or someone) very thoroughly.

   He's still new to their system, but he knows databases inside and out and will understand the rest soon.

• know backwards
• know like a book
• know like the back of one's hand

• inside out
• ins and outs