How to draw a straight line without a ruler?

How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net

How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net
How to draw a straight line without a ruler? Seen On  www.coolpicturegallery.net