(The Hammer Editor was used to make maps for Source games, The Stanley Parable included. The standalone game is built upon Portal 2)
How to find it
Note that you need Portal 2 and its Authoring Tools for this to work!
- Go to the game folder for The Stanley Parable. (SteamApps\common\The Stanley Parable\thestanleyparable)
- Copy the materials folder to the game directory for Portal 2
- Start the Portal 2 Authoring Tools, then go into Hammer.
- Go to the Textures Tab, click on the Keywords. It will say; "Stop looking through the game files, you nerd!"