Slang and idioms can be very confusing for nonnative speakers. Imagine if an American said to you, "Could you please crack the window?" You are NOT being asked to "break the window" (which is indeed the literal meaning). You are simply being asked to "open the window a little." Or if someone tells you to "Knock it off!" or "Cut it out!" - that just means "Stop doing that!" (which is something you commonly hear parents tell their children if they misbehave!). This book was written by American native and slang expert Slangman David Burke, author of more than 30 books on slang and idioms.