Idiom Magic : NAIL DOWN (2) 準確地說明

【明報專訊】"If vampires don't exist, how do you account for(解釋)the one Uncle Felix caught in our garden?" Teddy asked. "Can you nail down your description of that vampire a little more exactly? I mean, tell me what it does and what it looks like?" "Oh, it's just a typical vampire, the kind you see in the movies," Teddy answered. Nail down here refers to giving a clear and precise description(描述)of someone, a situation, a problem, etc.