If the value is 1, each vertical grid unit is intersected by a line of horizontal grid points. If the value is greater than 1, every nth vertical grid unit is intersected by a horizontal line of grid points, where n is the value of GRID-FACTOR-VERTICAL. The default value is 6.
The height of a vertical grid unit is defined by the GRID-UNIT-HEIGHT-CHARS or GRID-UNIT-HEIGHT-PIXELS attribute.
Note: Setting this attribute to 1 has the same effect as setting the GRID-FACTOR-HORIZONTAL attribute to 1, because either setting makes all grid points visible in the frame.