Extend Entities
You can add to the length of
a sketch entity (line, centerline, or arc). Use Extend
Entities to extend a sketch entity to meet another sketch entity.
To extend
a sketch entity:
In an open
sketch, click Extend Entities 
on the Sketch toolbar, or click Tools,
Sketch Tools,
Extend.
The pointer
changes to 
.
-
Move the pointer over the
sketch entity to extend.
The selected entity appears
in red, and a preview appears in red in the direction to extend the entity.
If the
preview extends in the wrong direction, move the pointer to the other
half of the line or arc .
Click the
sketch entity to accept the preview.
To extend a sketch entity beyond the closest
entity, click to place the first sketch extension, drag towards the next
sketch entity, then click place the second extension, etc.
