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