Use `-setgrid 1` when you create the `listbox`.  Note that only one
widget can properly have setgrid set per toplevel.  See the `options`
man page for more information.  It works like so:

listbox .l -setgrid 1 -yscrollcommand [list .s set]
scrollbar .s -command [list .l yview]
pack .s -side right -fill y
pack .l -side top -fill both -expand 1
.l insert end one two three four five six seven eight nine ten LAST

*Note:* You may have only one widget per toplevel use `-setgrid`.