If you're working with Source SDK for game development or 3D modeling, you may need to export OBJ files for use in other software or projects. Here's a simple guide to help you through the process.

1. Launch Source SDK and open your project. Navigate to the model you want to export as an OBJ file.

2. With the model selected, go to the file menu and look for the 'Export' option. Choose 'OBJ' as the file format for export.

3. A window will pop up allowing you to specify the export settings. Make sure to select the appropriate options for your needs, such as texture coordinates, normals, and material options.

4. Choose a destination folder and file name for your OBJ export, and click 'Export' to save the file.

5. Once the export is complete, you can use the OBJ file in other 3D modeling software, game engines, or any other project that supports the OBJ format.

Keep in mind that Source SDK may have specific requirements or limitations when exporting OBJ files, so it's always a good idea to consult the documentation or community resources for additional tips and best practices.

With this simple process, you can easily export OBJ files from Source SDK, and incorporate them into your game development or 3D modeling workflow. Happy exporting!