http://purl.org/tcl/home/man/tcl8.4/TkCmd/scale.htm

Scale-widgets are used for numeric input.
They work somewhat similar to sliders.
They don't cause text to scroll, 
but they adjust numbers by moving the button of the slider.

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See also: 
   * [poor man's progressbar]
   * [Widgets on a canvas]

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[Category Command] - 
[Category Widget] - 
[Tk syntax help]