[sdiy] modular rack systems?

[Barry Klein]

I'm confused... Recently there was this youtube
video on the tiptopaudio rack system.  It looked like
the rails were pre-tapped.  And yet rails are commonly
available with channels for captive nuts.  Why would
a pretapped solution be preferrable?
http://www.tiptopaudio.com/zrails.php
http://www.tiptopaudio.com/zearrck.php
http://www.youtube.com/watch?v=H22XIC3PO4I


Barry