When you first start the interface builder, a new interface is created for you automatically. You can also choose File > New or click on 
to create a new interface. A blank Common LispWorks window, known as the interface skeleton , appears on-screen, as shown in Skeleton Common LispWorks window. The interface skeleton contains no layouts or panes, or menus.
Figure 15.2 Skeleton Common LispWorks window
You can use File > New to create as many interfaces as you want; they are all displayed as soon as you create them. Since you can only work on one interface at a time, use the History > Items submenu to switch between different interfaces that are currently loaded in the interface builder.
As an alternative, type the name of an interface directly into the Interface text box and press Return to create a new interface, or to switch to an interface which is already loaded.