fly fishing nail knot

I wondered if I had to use a leader of fly fishing every time you attach a new fly?
I a new cane with everything you need to fish with thei, I tied a good knot nail connection with the leader of the line (and wasen't easy) and fly to the leader. I do not know is if I attached a new leader to the line every time I want to spend a fly?
NO! Attach a 2 or 3 foot tippet at the end of the leader, then tie the fly on the tippet. Tippet is evaluated by the coil diameter. When the pilgrim brothers or exchange for keeping the flies, just tie a cape again.
How to tie a Nail Knot
