position	Rectangle on the screen to use for the scrollbar.
value	The position between min and max.
size	How much can we see?
leftValue	The value at the left end of the scrollbar.
rightValue	The value at the right end of the scrollbar.
style	The style to use for the scrollbar background. If left out, the horizontalScrollbar style from the current GUISkin is used.

Returns
float The modified value. This can be changed by the user by dragging the scrollbar, or clicking the arrows at the end.

Make a horizontal scrollbar. Scrollbars are what you use to scroll through a document. Most likely, you want to use scrollViews instead.

	var hSbarValue : float;
	
	function OnGUI () {
		hSbarValue = GUI.HorizontalScrollbar (Rect (25, 25, 100, 30), hSbarValue, 1.0, 0.0, 10.0);
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public float hSbarValue;
    void OnGUI() {
        hSbarValue = GUI.HorizontalScrollbar(new Rect(25, 25, 100, 30), hSbarValue, 1.0F, 0.0F, 10.0F);
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public hSbarValue as float

	def OnGUI() as void:
		hSbarValue = GUI.HorizontalScrollbar(Rect(25, 25, 100, 30), hSbarValue, 1.0F, 0.0F, 10.0F)

Finding extra elements:

The styles of the buttons at the end of the scrollbar are searched for in the current skin by adding "leftbutton" and "rightbutton" to the style name. The name of the scrollbar thumb (the thing you drag) is found by appending "thumb" to the style name.

	var scrollPos : float = 0.5;
	// This will use the following style names to determine the size / placement of the buttons
	// MyScrollbarleftbutton    - Name of style used for the left button.
	// MyScrollbarrightbutton - Name of style used for the right button.
	// MyScrollbarthumb         - Name of style used for the draggable thumb.
	function OnGUI() {
		scrollPos = GUI.HorizontalScrollbar(Rect(0,0,100,20), scrollPos, 1, 0, 100, "Scroll");
	}