Prevent drop of list item in JqueryUI sortable

Question

I have two lists #sortable1 and #sortable 2 which are connected sortables, as shown in this example.

You can drag and drop list items from

Answer 1

beforeStop: function(ev, ui) {
                if ($(ui.item).hasClass('number') && 
                    $(ui.placeholder).parent()[0] != this) {
                    $(this).sortable('cancel');
                }
            }

try this.