The
saying “know (something) like the back
of one's hand” means to be intimately knowledgeable about something,
especially a place – See the example below.
For Example:
“He knows the
software like the back of his hand,
and can often solve problems over the phone, without looking.”
This is the Idiom #69 in the List of 100 commonly used Idioms in everyday English (Top 100 famous Idioms). By introducing this list of notable idioms to English learners and ESL students as you, we believe that your English will sound more like a native and you can easily understand what native speakers are saying. Please like and share this list with your friends if you think it is helpful - the full list is here.
 like the back of one's hand ” means to be intimately knowledgeable about something , especially a place...){kind=link}