Which are the structural design patterns?

Adapter: The Adapter pattern is used to adapt an interface of one class so that it can be used by a different class that originally could not use it. The adapter is sometimes called a wrapper. For example, adapters or wrappers are often written for existing libraries so that a new application can use the library.
Bridge: A Bridge is used to decouple an abstraction from its implementation. The Bridge pattern is often used to build drivers, such as a printerdriver, which connect an application program with a real printer.
Composite: The Composite pattern is used to compose whole-part hierarchies into tree structure that will let the client treat either the individually objects, or compositions of those objects uniformly.
Decorator: The goal of the Decorator pattern is to add more responsibilities to an object dynamically, and avoid subclassing. An example is adding scrolling to a text view. The scrolling object surrounds the text view, handles the mechanics of the scroll bar, and then tells the text view to display itself appropriately.
Facade: The Facade pattern provides a higher level unified interface to a set of objects in a subsystem. The extra layer provides a simpler interface to the subsystem, and helps to avoid coupling between classes.
Proxy: The Proxy pattern is similar to the Adapter in that it provides an interface layer between objects. While an Adapter will change the  interface, a Proxy doesn't change the interface, but instead will control the access to one object from another.