When StreetDeck is installed it binds the *.sdu and *.sdz file extentions to the main program.
An SDU file extention is a StreetDeck patch file. It a special packed file that can contain images, executable code, or anything else to be installed into the StreetDeck directory needed to correct a bug or add additional internal functionality. SDU files can be downloaded and placed onto a thumbdrive or transferred to your StreetDeck system in any manner you want. When double clicked on a StreetDeck system, the file will automatically attempt to patch the installed version of StreetDeck if and only if it detects an older version is installed. If a SDU file is copied to the root directory of a thumb drive or CD, and inserted into a StreetDeck system while StreetDeck is running, StreetDeck will automatically detect and install the update and restart.
An SDZ file is a zipped StreetDeck Package file. It is a special type of compressed file that can contain any number of things, other then patches, that are not related to the core functionality of StreetDeck. Usually an SDZ file contains a new skin or a scripted module. Similar to SDU files, SDZ files can be double clicked on a StreetDeck system or inserted while StreetDeck is running to install its contents.