When this setting is enabled the content of the tree will be wrapped by borders.
Examples
Material Design True
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         border: true,
         checkboxes: true
     });
 </script>
  
  
Material Design False
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         border: false
     });
 </script>
  
  
Bootstrap 3 True
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap',
         border: true
     });
 </script>
  
  
Bootstrap 3 False
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap',
         border: false
     });
 </script>
  
  
Bootstrap 4 True
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap4',
         border: true
     });
 </script>
  
  
Bootstrap 4 False
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap4',
         border: false
     });
 </script>
  
  
Bootstrap 5 True
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap5',
         border: true
     });
 </script>
  
  
Bootstrap 5 False
    
 <div id="tree"></div>
 <script>
     $('#tree').tree({
         dataSource: '/Locations/Get',
         width: 500,
         uiLibrary: 'bootstrap5',
         border: false
     });
 </script>