This simple example simply resizes a single box using a sizing grip at the bottom of the window. Note that .resizable() does not handle of the UI aspects - it only manages the actual resizing operation itself. You're responsible for creating placing the sizing handle where it makes sense for your UI.
To apply resizing use the .resizable plugin and specify the resizable container and a sizing handle that initiates resizing:
$(".box").resizable({ handleSelector: ".win-size-grip"});
Note that you can also use the initial container for resizing by reapplying the initial selector but usually provides