Simon - are you asking how we attach a single strand bite leader to the end of a twisted leader?
If so, you can either tie it on or you can crimp it on. Tying it takes some practice as you need to nail knot the heavy bite leader but you can use a simple uni knot for the twisted leader. Neil showed me how to nail knot it a while back - it is hard to explain without seeing it. Crimps are the easiest.