So yesterday, I bought myself Black Mesa: Source on Steam, Partly so I can play half life with the Improved graphics, Partly because It was on Sale, And Partly so I can play the Black mesa source RP maps on Gmod (Singleplayer, I'll never play any non Nebulous RP servers). The one problem is, I can't seem to accomplish the last part. It isn't anywhere in the Game mounting menu, But I know it can be done, because there are maps that say you need to mount Black Mesa Source in order to play them properly. So my question is, Is there a way to mount the Steam Edition of Black Mesa Source Onto Garry's mod? Please tell me if anyone knows.