A single player map by Flynn2.
All of the files will go in a folder with the following path:
C:program filesValveSteamSteamapps(the name of this folder depends on your Steam username)Half-Life 2hl2
The .bsp file goes in the "maps" folder.
All files ending with .vmt go into the materials folder.
To play the map:
In order to play the map, you need to enable the Half-Life 2 "console". To do this, right click on Half-Life 2 and select "properties". Click on "Set launch options" put -console in the launch options box.
You can also do this for the Half-Life 2 shortcut on your desktop.
Start Half-Life 2. A window will come up with lots of text in it. Underneath it there will be an area where you can enter text with a button saying "submit" on the right. In here, type map corridors and it will load the map.