know it like the back of my hand

What it means

To 'know something like the back of your hand' means to be extremely familiar with it, every detail and corner included. It's often used about places, routines, subjects, or people you've spent a lot of time with. The phrase implies confidence that you couldn't get lost or confused.

Examples

• I grew up in this neighborhood, I know it like the back of my hand.
• Don't worry about getting lost on the trail, our guide knows it like the back of her hand.
• After twenty years of teaching this book, I know it like the back of my hand.
• Ask him about jazz history, he knows the subject like the back of his hand.

Where it comes from

The phrase draws on the idea that the back of your own hand is something you see constantly and could recognize anywhere. It became a common English expression in the 20th century to convey deep, intimate familiarity.

Related idioms