The most common technique of tying more that one fly to a leader involves the use of droppers. These are short three to six inch lengths of line protruding from the main leader length. A full-blood knot was once the recommended method of dropper creation. However, since the introduction of pre-stretched nylon and co-polymers, three-turn water knots are now standard. The water knot (AKA surgeons loop / Cove knot) creates two possible dropper lengths. Use the downward length - the one pointing towards the end fly - since this is stronger one.

NB "dropper" is often the word given to the fly itself. On a three fly set-up, starting from the end, you have the point fly, middle dropper and top dropper. The top dropper is often referred to as the "bob fly".

In New Zealand they often forego this short length of line and attach the leader directly to the bend of the hook. This technique has it's followers outside of NZ as well.