Map Labs is an ongoing anthology of Half-Life 2 levels designed for the various Map Labs mapping challenges.
Mapping challenge were entrants were to make dev texture maps.
This is a sourcemod that uses the Source 2013 Singleplayer SDK. To install, place the "blockout" folder inside your "sourcemods" folder which can be found under "C:\Program Files (x86)\Steam\steamapps\sourcemods" if you are using the default steam install path.
Then you need to make sure you have installed "Source SDK Base 2013 Singleplayer" under the tools section of your steam library, then you also need to make sure that you have set it to the "upcoming" beta. You can do this via right clicking on the SDK, selecting "Properties", then "Betas" and lastly selecting "upcoming".