Something

import Tkinter

class Vrule(Tkinter.Frame):
    def __init__(self, *args, **kw):
        kw['borderwidth'] = 1
        kw['relief'] = Tkinter.SUNKEN
        kw['width'] = 2
        Tkinter.Frame.__init__(self, *args, **kw)
        
app = Tkinter.Tk()
toolbar = Tkinter.Frame(app)
toolbar.pack(side=Tkinter.TOP, fill=Tkinter.Y)

button1 = Tkinter.Button(toolbar, text="b"); button1.pack(side=Tkinter.LEFT)

div = Vrule(toolbar)
div.pack(side=Tkinter.LEFT, fill=Tkinter.Y, padx=4, pady=4)

button2 = Tkinter.Button(toolbar, text="B"); button2.pack(side=Tkinter.LEFT)

app.mainloop()