GUILayout.EndVertical  

function OnGUI () {    
    GUILayout.BeginVertical ("box");

    GUILayout.Button ("I'm the top button");
    GUILayout.Button ("I'm the bottom button");
    
    // End the vertical group we started above
    GUILayout.EndVertical();
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnGUI() {
        GUILayout.BeginVertical("box");
        GUILayout.Button("I'm the top button");
        GUILayout.Button("I'm the bottom button");
        GUILayout.EndVertical();
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnGUI():
        GUILayout.BeginVertical('box')
        GUILayout.Button('I\'m the top button')
        GUILayout.Button('I\'m the bottom button')
        GUILayout.EndVertical()