Often extracted using GCFScape for use in Source Filmmaker or 3D printing.

Ensure every numbered part of the "sc23780-TF2" set is in the same directory on your computer.

To successfully open it, you must have all previous and subsequent parts (part 1, 2, 4, etc.) in the same folder. How to Extract the Content

Custom game modes or visual enhancements for your local TF2 folder.

The file is one piece of a multi-part compressed archive likely containing Team Fortress 2 (TF2) assets or community-created content. Understanding Multi-Part Files

Right-click only on sc23780-TF2.part01.rar and select "Extract Here" . The software will automatically pull data from all other parts, including part 3, to reconstruct the full original file.

Do you have of the archive downloaded in that same folder?

Windows does not natively extract .rar files. Download and install a tool like 7-Zip or WinRAR .