Its Symbolism
¥On the website "Myk's Wanderings" at www.freewebs.com/mykal-laws/themeaningofshape.htm, the author explains the symbolism of straight lines:   
¥The line is a symbol of boundary and division.    A straight line represents infinity because it can continue in either direction indefinitely.  A vertical line represents the spiritual world and a horizontal line the temporal world. 
¥     The horizontal line represents the path of birth to death, beginning to end, and the dual nature of man...left and right,good and evil, and male and female.  The feminine principle.
¥     A vertical line symbolizes man, the body, the spine, the tree of life, and the path from earth to heaven...the realm of the spirit.  The masculine principle.