know somebody/something inside out
US /noʊ ˈsʌm.bə.di ˈsʌm.θɪŋ ˌɪn.saɪd ˈaʊt/
UK /noʊ ˈsʌm.bə.di ˈsʌm.θɪŋ ˌɪn.saɪd ˈaʊt/

1.
conocer al dedillo, conocer a fondo
to know someone or something extremely well
:
•
She's worked here for twenty years, so she knows the company inside out.
Ha trabajado aquí durante veinte años, así que conoce la empresa al dedillo.
•
He's a local, so he knows this area inside out.
Es de aquí, así que conoce esta zona al dedillo.