How do I join two mkv's?

[dubious buccaneer]

I've heard I can use AVIMux to join two mkv's, but I haven't found such an option anywhere in the GUI. What do I do?

I have two segments of a video file, with their respective subtitles, each in its own mkv, and I want a single file for the whole movie.

(If you intend to recommend that I demux them and join the components, then please tell me how do I join 2 .sub+.idx file pairs)

[multicone]

http://www-user.tu-chemnitz.de/~noe/Video-Zeug/AVIMux%20GUI/en_join_files.html

[dubious buccaneer]

Thanks, I was just missing the 'Ctrl-Click' part. Maybe this could be added to the relevant part of the FAQ?