If you need to use different Job Card templates depending on the type of work or make of car then Onyx gives you the choice, but only after you have set it up:

From the Options screen, press the button labeled 'Add Custom Job Cards' and the following screen will be displayed:

Simply click in the row labeled 'Click here to add a new item', enter a unique caption and then select the appropriate template using the browse button:

Please note that you will have to press the down cursor key to accept the very first entry, subsequent entries can be accepted by clicking in a different row.

Now when you go to print a job card you can also select from your new entries: