guideX(x)
Creates a vertical guide line at the current spread and current layer.
Type: function
Parameter(s):
- x {Number}:Position of the new guide line. 
Returns:
- 
    {Guide}:
 New guide line. 
Creates a vertical guide line at the current spread and current layer.
Type: function
Parameter(s):
Position of the new guide line.
Returns:
New guide line.