Blender: how to make an edge flush with another edge by snapping and scaling

Making an plane edge geometry flush with another plane geometry is a typical CAD task. In Blender 3D, it is possible to do the same using simple Move and Scale commands, but with the right settings. 

The screenshot below shows 2 plane objects in the top view. This post shows the steps to adjust the bottom plane to snap nicely to the plane on the left.

Set to Snap to Vertex

1.  In the Blender 3D Viewport menu bar, click the Snap icon and choose Vertex as shown below.
   
   
   
   
   

Snap the vertex of one plane to the vertex of the other plane

1. In the Blender 3D Viewport, make sure the Edit Mode is enabled and Select Mode is Vertex.
   
   
2. In the Blender Toolbar, select the Move icon. Then click on the bottom vertex of the plane to be moved.
   
   
3. On the keyboard, press down CTRL and drag the bottom vertex to snap to the vertex of the other plane.
   
   
    

 Scale the edge vertices by axis to zero

1. In the Blender 3D Viewport menu, set the Transform Pivot Point to Active Element as shown below.
   
   
   
   
    
2. On the keyboard, press ALT-a to deselect all selection.
   
   
3. In the Toolbar, click the Select Box icon.
   
   
   
   
   
4. Click the top vertex of the plane to be scaled.
   
   
5. Press SHIFT and click the bottom vertex.
   
   Note: since the Transform Pivot Point is set to Active Element, the scaling will be relative to the last selected vertex.
   
   
6. Press S.
   
   The plane scales dynamically around the last selected vertex as the cursor is moved.
   
   
   
7. Limit the direction of scaling to the X-axis (in this example) which is perpendicular to the matching edges. Press X.
   
   The plane can only scale along the X axis.
   
   
   
8. Press 0.
   
   The planes are snapped nicely to one another.