Swap/Remap Ctrl and Alt keys

[Young]

Kazuo Ishii wrote:
> There are several ways to swap keymap.
> Refer below.
> You can swap it in X and console.
>
> http://www.uluga.ubuntuforums.org/showthread.php?t=633403
>
> 2008/6/8 Young <tuxman at knology.net>:
>   
>> Has anyone been able to swap the Ctrl and Alt keys?
>>
>> That swap would make it more like a Mac when using the keyboard commands.
>>
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>>     

That discussions was hard to follow. I couldn't get anything out of that 
I could try to use.
Have you switched the keys (Ctrl and Alt) yourself? Or something similar?