This page (MSDN) says in the first step:
Alternatively, you can also use configuration to add an AJAX endpoint.
I’m unable to access my service endpoint following their example exactly. (VS2010, .NET 4.0, Win7) I always come back with 404-not found when I try to access it.
You can define the endpoint using configuration, but you need the .svc file to host the file in IIS.
If you really don’t want an .svc file, you can also use the the ASP.NET Routes integration (more info in http://blogs.msdn.com/b/endpoint/archive/2010/01/25/using-routes-to-compose-wcf-webhttp-services.aspx or http://msdn.microsoft.com/en-us/library/ee662952(VS.100).aspx) – in that case you’ll specify the factory when you’re setting up your route.