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

If a) you only have just these 2 lists, and b) you don't care that your "number" actually be dragged and then drop back, you can simply prevent it from getting dragged by this:

 sort: function(event, ui) {
if(ui.item.hasClass('number')) return false;
}