Resizing or Reshaping Objects
To change the length of an object by dragging
- From the Modify toolbar, choose Lengthen.
- Enter dy to enter Dynamic Dragging mode.
- Select the object to lengthen.
- Drag the endpoint closest to the point of selection and specify a new endpoint using any point entry method.
The selected object is lengthened or shortened without changing its location or orientation.
Modify toolbar: 
Command line equivalent: LENGTHEN