Lock to avoid dragging in sortable

Question

This week I received the help of Lucio Rubens with a doubt, he helped me with this code, to get the Ids of the elements clicked.

Now on top of this same code, I need to lock a UL so that it does not allow more elements to be removed,

This is the working example, Jsfiddle.

$(".items").sortable({
    connectWith: ".items",
    receive: function(event, ui) {
        var id_origem = ui.sender.attr("id"),
            id_clicado = ui.item.attr("id"),
            id_destino = $(this).attr("id");
    }
});

Answer 1

In the example in the link below, I inserted a block class not to allow the withdrawal of it, in this way, it receives the items but does not leave it.

http://jsfiddle.net/sw4gs7nh/