Registering external forms (SWF files) in Arp

I just got a question on the Arp list about how best to register external forms (external SWF files) with your main application and it reminded me that this information is only available in an email I sent to the OSFlash list a while ago.

So, to make it more visible, here's a link to that:

How to work with external forms (external SWF files) in Arp.

The code in there is for Flex 1.5 but the technique is the same regardless of whether you're using Flash, AS2, AS3, Flex 1.5 or Flex 2.