What a time for a book about computers! Machines are faster than ever, with some systems clocking in at more than three gigahertz. Yet, amazingly, they cost less than ever before, too. You can buy a new personal computer for less than $300—at least if you turn over rocks for the best prices and look for a free operating system (which is sort of like buying a car and curb-surfing for tires).
Source: The Winn L. Rosch Hardware Bible
I don't understand what that means.
This is a reference to “leave no stone unturned.”
leave no stone unturned
to do everything you can to achieve a good result, especially when looking for something:He left no stone unturned in his search for his natural mother.
Source: Definition of “leave no stone unturned” from Cambridge Dictionaries Online
The idiom comes from Heraclidæ, a tragedy written by Euripides around the year 428 BC.
Previous answers have cited sources that define but do not explain the term "leave no stone unturned"; it may be easier to remember with a bit of visual background:
Imagine that you are looking for a valuable coin that was dropped in a field ten years ago. You won't just look in every centimeter of the field, you will pick up every rock to look underneath it. Once you've done that, you have, literally, left no stone unturned.
To turn over rocks for something means to do a lot of hard work to achieve something.
It means it takes time, hard work patience and persistence to find something of value.
Strategic Leaders Turn Over Rocks to Find Gems
