Ensure you have the Source Engine game(s) you wish to mount fully installed and up to date and have ran the game at least ONCE before continuing.

• Start Garry's Mod (or press ESC) so you can see the Main Menu.
  
  
  
• Click the controller icon () down the bottom, next to the language icon.
  
  
• Tick which games you wish to have mounted.
  
  
  
• You may need to Restart Garry's Mod. (Close and Reopen the Game)
  
  
• That's it! You have now successfully mounted the games!

NOTE: Mounting a lot of games may cause slower start up times and slower connection times to servers. It is recommended you only mount what you need.

NOTE: Only Source Engine games which have been approved and set up by Garry will appear on the list. Example. Warframe is not Source Engine: so it will not be on the list.

This section provides information on the icons.
Game Not Installed.
Game Not Owned (or Disabled by Garry).
Game Not Mounted, But Able To Mount.
Game Mounted.

This may not be correct as there is no official information on the icons Garry has used.

This is an additional section to help people who wish to select only what they need.

(Un-modified) DarkRP

• Counter-Strike: Source

May Vary from Server to Server

Deathrun

• Counter-Strike: Source

Elevator: Source

• Half-Life 2: Episode 2

GMod Tower

• Counter-Strike: Source
  
• Half-Life 2: Episode 2
  
• Team Fortress 2

Half-Life 2 Roleplay

• Counter-Strike: Source
  
• Half-Life 2: Episode 2

May Vary from Server to Server

Post Nuke RP

• Counter-Strike: Source
  
• Half-Life 2: Episode 1
  
• Half-Life 2: Episode 2

Prop Hunt

• Counter-Strike: Source

May Vary from Server to Server

Trouble in Terrorist Town

• Counter-Strike: Source

May Vary from Server to Server

Zombie Survival

• Counter-Strike: Source

May Vary from Server to Server

Most Maps (skyboxes, textures, etc)

• Counter-Strike: Source

If you wish to have a gamemode added, please add a comment.

A game isn't working, or I see purple checkerboards, weapon or world models are missing, or experience crashes while playing a game - how can I verify that my game files are installed correctly?

Try following this Steam Knowledgebase Article:

• https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335

If you're sure you've read over everything and it's still not working and you have tried verifying your cache or are receiving unexpected errors, your best bet is to Contact Support.

• Support for Garry's Mod, (via Facepunch Studios): For Garry's Mod Issues, mounting, etc.[support.facepunchstudios.com]
  
• Official Steam Support: For Cache Issues, and Other Steam Related Issues.

You can purchase the games mentioned above with the links below, bundles are a quick way to get a lot of games and save money. Otherwise, if you just want the individual game, click on it's individual link.

The Orange Box $19.99 USD (Save $15.97 USD)

If this guide has helped you, please help this guide back by giving it a thumbs up.

If the guide hasn't helped you, I'd firstly like to apologise and secondly, leave a comment below and I'll attempt to help you; but if you have followed it top to bottom your best bet would be to try and contact the appropriate support as that's what you paid them for.