Modify: Trim

Description:

Trims or extends a line, arc or ellipse to another entity.

Procedure:

1. Choose the limiting entity to which you want to trim or extend one or  more other entities.

2. Choose the entities that you want to trim to the limiting entity. Often  there are two possibilities for the entity to be trimmed. In the example  below, you might want the top part of the line to remain in the drawing and  the lower part to be trimmed away. In that case you would have to click the  trim entity at the upper part. Always click that part of the entity which you  want to remain.  
   

3. Right click twice or press Escape twice to terminate the tool.