No gamemodes/sandbox? Fading Door help.

Hi, first post, sorry if everything I say is noobish as hell.

I downloaded the Fading Door Tool from garrysmod.org, and it says to extract it into garrysmod/garrysmod/gamemodes/sandbox/entities/weapons/gmod_tool/stools. Well, I went into garrysmod/garrysmod/gamemodes, and all that was in there was a blank text document called “gamemodes.txt.” Since I couldn’t quite follow the directions exactly, I just put the file in the addons folder. Yeah, that didn’t work.

So, uh, what do I do? Are the instructions out of date or is my gmod folder screwed up? I can still play sandbox in Gmod, so I don’t quite know why it’s not there…

Create the folders needed. If that doesn’t work then it’s because the tool just doesn’t work due to age (the fading door tool is seriously old).
Try finding a more modern equivilant or something.