Why are rom files double zipped?

[namelessme001]

I recently downloaded a rom file from the psx section and when I extracted it using 7z all I got was a 001 file. I tried extracting this 001 file with 7z but it said the file was non-existent. What am I suppose to do with this?

[GameGeeks]

If it has 001, ect after the extention it means it's a split archive and you need to merge it. Follow the guide in PC support, except go to 7-zip when you go to extract it.

[namelessme001]

If it has 001, ect after the extention it means it's a split archive and you need to merge it. Follow the guide in PC support, except go to 7-zip when you go to extract it.
I don't see a thread title indicating such a guide on that forum. The thread title would be helpful...

[GameGeeks]

It's titled merging split archive files.

[namelessme001]

It's titled merging split archive files.

Gee thanks for telling me the thread title.