Other options:
- press 
SHIFT to set the second point, this enables 15° snap and gives exact horizontal/vertical lines too
- use the command line, set first point, then enter 
@100,0 - that sets the endpoint 100 to the right horizontally (because Y=0)
- or enter 
@100<90 - 90 is the angle and creates a vertical line
	
	
	
				investing less than half an hour into Search function can save hours or days of waiting for a solution