jQuery UI is a library that uses jQuery to provide an easy way to implement user interactions with your web page. The Sortable plugin allows users to click and drag an element to rearrange its position on the page.

It works by calling sortable on a jQuery object. This will make all the immediate children of that HTML element sortable.

In Backbone, you should put this at the end of the render function of your views. It's important to note that this sortable function call will not work properly unless the elements have already been inserted into the DOM. Thus, you should make sure that your router first sets the HTML appropriateley, and then calls render.

You should also make sure that you call the sortable function on any element that needs it any time any of its parent views has been re-rendered. A good way to do this is to move the sortable call into a separate onRender function. This function should a) call sortable on the appropriate element, and b) recursively call onRender on all its subviews.