​Limiting access to features on devices such as iPads when using them for Kiosks or for use
as  a Point of Sale Station requires the use of Apples Guided Access.  Guided Access limits your iOS device to a single app and lets you control which features are available. 

​Guided access also prevents the Apple devices from being used in ways you may not intend when you are not watch such as surfing the internet or using other apps. 

Guided access is very simple to setup in just a few steps 

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To Set up Guided Access

1. Go to Settings > General > Accessibility > Guided Access.
2. Turn on Guided Access. (it should be a choice at the top of the screen) 
3. Tap Passcode Settings, then tap Set Guided Access Passcode.

Start a Guided Access Session

1. Open the app that you want, then triple-click the Home button. 
2. If you want parts of your screen to stop responding to touch, use one finger to circle those areas. You can move or resize the circle, or tap the X to remove it.
3. Tap Start. 

See more steps at ​https://support.apple.com/en-us/HT202612