Another way the shell can be extended is by custom property sheets. When the user selects the properties for a file, the shell displays a standard property sheet. If the registered file type has a property sheet handler, the shell allows the user to access additional sheets that the handler provides. Property sheet handlers implement the IShellPropSheetExt interface.
Property sheet handlers are entered in the registry under the shellex key within an application's information area. The PropertySheetHandlers key lists the names of subkeys that contain the class identifier of each context menu handler, as shown in the following example.
PropertySheetHandlers
{00000000-1111-2222-3333-00000000000002}
You can register multiple property sheet handlers for a file type. In this case, the order of the subkey names in the PropertySheetHandlers key determines the order of the additional property sheets. You can use a maximum of 24 (the value of MAXPROPPAGES) pages in a property sheet.