Limit an IOS 6 Device to Running only ONE app! Guided Access for iPad

With Apple's IOS 6, you now have the ability to limit an iPad  to the use of a single app, and turn it off and on as needed. Here's how...

In the General Settings of your ipad, click Accessibility and turn ON 'Guided Access' and set a passcode.

To use this feature, open the app you want to use, and Triple-Click the home button.    
Tap the Start button. 

To turn off Guided Access, triple click the home button again and enter your passcode.