[header] How to create a pattern in adobe illustrator [title] Create a new square by using the rectangle tool, set it at 200x200px. [title] Change the square into a triangle by using the delete anchor point tool and click at the top left point. [title] Click on the triangle and go to the reflect tool. 
[step] Hold down the alt key and click on the position that you need to be a center of a reflection. Select vertical axis and click " ok ".