Victims are usually forced to work through a combination of fear, intimidation, abuse, and other forms of psychological manipulation. For example, traffickers may convince workers they're in monetary debt to the trafficker (usually for transporting, housing or feeding the victim), and cannot be freed until that debt is paid off.
To further control victims, traffickers might restrict workers' access to their own money or identification, surround them with heavy security and escort them wherever they go, or force them to live where they work.