If you need to lengthen a line, especially if the line is at an angle other than horizontal or vertical, this command is for you. It will lengthen a line and keep it in the angles that it originally was. Usually, if you select a line that is at an angle and then click a grip to lengthen it, you will not be able to keep the angle. (Note: in AutoCAD 2012 select a line and then hover over and endpoint grip and you will see the option for LENGTHEN.)
- LENGTHEN <enter> or LEN <enter>
or on the ribbon:
- Home Tab > Modify Panel > Lengthen button (in the drop-down) as seen below.
- After starting the Lengthen command, notice that there are options in the command line.
- DY <enter> to star the “dynamic” function of the lengthen command.
- select the side of the line that you would like to lengthen or shorten.
- after selecting the line, move your cursor in the desired direction and either click to end the “lengthening” or enter a number.
In the animated example, I lengthened and shortened the lines by six inches
AutoCAD Tips 
Pingback: Lengthen Polyline Endpoint & Vertex | AutoCAD Tips
omg..thank you so much. I always do angled lines line this and was never able to lengthen it the simple way. This helped me so so much. Thanks!
What Priya said. Very helpful lil’ tip, cheers!