CMS.CMSHelper.TreeHelper class provides useful methods that allow you to access documents. All methods are static, which means you can access them directly like CMS.CMSHelper.TreeHelper.SelectNodes.
| SelectSingleNode | Returns single node (document) specified by given NodeID or path. | 
| SelectSingleDocument | Return single node (document) specified by given DocumentID (culture-specific document version). | 
| SelectNodes | Returns a DataSet object containing nodes (documents) of given path. | 
Page url: http://devnet.kentico.com/docs/5_0/devguide/index.html?treehelper_class.htm