How to create a bundle file from .crt-files?

A number of systems (including Apache) require that the intermediate certificates must be collected in a bundle file.
This can be done easily by creating a new text file containing all intermediate and root certificates in “reverse”:
Intermediate 2
Intermediate 1
Rot 0
(Note! You can get wrong Chain Anchor by having the top root in bundle as this should be in the operating system / client from earlier, then you can only remove the last (root) from the bundle.
Save the file as yourdomain.ca-bundle. We have finished making bundle files for all our certificates HERE.