##
slider.vertical()

    sl.vertical(true | false | () )

Toggles the slider from a vertical to a horizontal display or vice versa. The effect is the same as shift-clicking the slider's title bar.
Like all functions of this kind, the "vertical()" method can be called in three ways: without a parameter, in which case it returns the actual status of the menu as a boolean, or with one parameter: true or false, in which case it c$sets it. Toggling can be done by

    sl.vertical ( ! sl.vertical() )