I could have hit you in the head with a rock just now.
Then one hand comes up with a rock, and I close my eyes.
"A little girl hit me with a rock when I was about six years old."
Even then, you couldn't hit the ground with a rock.
I was ready to break the glass with a rock.
"He looks as though he's been hit on the head with a rock."
"I hit one of them in the head with the rock."
A woman came with a big rock and hit it on the head of the security guard.
They then argue over what to do with the rock.
"If he attacks me I'll just hit him with a rock and call the police."