Working with Linked Vertices in Blender
A handy way to select things in Blender’s Edit mode is by selecting linked vertices. Linked vertices are a set of vertices within a mesh that are connected by edges. In order to understand linked vertices better, go through the following steps:
Select (right-click) your default cube in Blender and tab into Editmode.
All the vertices are selected. If not, press A until they are.
With all the vertices selected, press Shift+D or choose Add→Duplicate from the Tools tab in the Tool Shelf or Mesh→Add Duplicate from the 3D View’s header to duplicate your selection.
Blender creates a copy of your selection and automatically switches to grab mode, allowing you to move the duplicate set of vertices, edges, and faces immediately.
Use your mouse to move your new cube off the original and confirm your placement by left-clicking a second time or pressing Enter.
None of the vertices in the original cube are selected. Each cube represents a set of linked vertices. So what if you want to select all the vertices in that cube, too? Sure, you can use the Border, Circle, or Lasso Select tools, but on complex meshes, these tools can get cumbersome. Instead, move to the next step.
Place your mouse cursor near any vertex in the original cube and press L.
Blam! All the vertices in both of your cubes are selected.
Of course, the natural next question is, “How do I deselect linked vertices?” That’s just as easy. Place your mouse cursor near any vertex on the duplicate cube you created and press Shift+L. All vertices connected to the one near your mouse cursor are deselected. These hotkeys are very handy.
Quite a few more selection options are available to you when working with meshes.
While you’re in Edit mode, you can work only with the current active object. You can’t select and manipulate other objects while you’re in Edit mode.