When you get sent to "hole" in prison what does that mean and how long do they usually keep you there?

The "hole", also known as the SHU (special housing unit) is prison inside prison. The inmate is in a one or two man cell with zero access to the outside world except for two one-hour exercise periods where you are in a cage outside. It is strict, high security with 24/7 monitoring. Inamtes get three square meals per day and three showers per week, one 15-minute phone call per week and a very abbreviated commissary list. It is not the place that any inmate wants to find themselves.