Docs / WPF controls
Border
The border allows adding only one control within it. You can set up the border by following these steps:
Navigate to the TOOLBOX and drag the Border from it on the form.

Drag the control from the TOOLBOX, for example, Button into the Border.

You can further implement different layout properties onto it as described in:
Properties, Methods and Events
All of the properties, methods, and events can be found in Microsoft’s documentation at:
https://docs.microsoft.com/en-us/dotnet/api/system.windows.controls.border?view=windowsdesktop-6.0