How do you combine files from multiple discs?

[macdonjh]

I have one antique dual-sided DVD and several movies that are on two discs. How can I combine the two files MakeMKV creates into a single file for play back?

[Woodstock]

A search for "lord rings" here will come up with some solutions, usually revolving around the use of mkvmerge, part of the mkvtoolnix collection (you can find that with a search for "mkvtoolnix" on your favorite search engine.