Close a group started with BeginHorizontal.

	function OnGUI () {	
		GUILayout.BeginHorizontal ("box");
		GUILayout.Button ("I'm the first button");
		GUILayout.Button ("I'm to the right");
		
		// End the horizontal group we began above
		GUILayout.EndHorizontal ();
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnGUI() {
        GUILayout.BeginHorizontal("box");
        GUILayout.Button("I'm the first button");
        GUILayout.Button("I'm to the right");
        GUILayout.EndHorizontal();
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnGUI() as void:
		GUILayout.BeginHorizontal('box')
		GUILayout.Button('I\'m the first button')
		GUILayout.Button('I\'m to the right')
		GUILayout.EndHorizontal()