You have to exchange files/messages using AS2 with your trading partner tomorrow, and you do not know the AS2 (RFC 4130) transport protocol. On the other hand, you have experience transferring files/messages with FTP or HTTP (WebDAV).
Then, AS2Box is the solution to your problem!
An AS2Box is a simple folder structure with an "incoming" and an "outgoing" folders, which you can access via FTP or WebDAV.
We manage the AS2 connectivity with your trading partners.
The messages that your trading partner sent to your AS2Box will be received into your "incoming" folder, while the messages you upload to your "outgoing" folder will be picked up and sent to your trading partner.