smoke33, there was a recent thread that went over this subject pretty thoroughly, but from reading your question I think you may not understand the terminology yet.
The terminology for a complete line setup on a fly rod starting from the reel spool is;
Backing - usually dacron in 20 or 25 pound test line attached to reel with an arbor knot.
Fly line - usually a PVC covered line which attaches to the backing. Usually with either a loop to loop connection or using a nail knot.
Leader - usually tapered in Nylon or Flourocarbon or braided leader. Attaches to fly line usually with a loop to loop connection or a nail knot.
Tippet - usually Nylon or flourocarbon. Attached to the end of the leader. Size dictated by the fly being used and the diameter of the end of the leader.
Tippet should never be larger in diameter than the end of the leader. So if the leader ends in 5X then the tippet should be 5X, 6X or 7X but never 4X. Because the leader is tapered it can be cut back to a thicker section if you desire to use 4X tippet or you can just buy a 4X leader.
The tippet to leader connection is usually made with a blood knot or a double or triple surgeons knot.
A leader can have a small metal ring on the end called a tippet ring. You can tie tippet directly to the tippet ring with a clinch knot (or whatever your favorite knot is).
The term Nylon is the material used in Monofilament fishing line sometimes referred to as mono.
No Knot eyelets are not a good solution in my opinion as inserting a solid piece of metal in to the fly line to leader connection causes a hinging effect in the cast and they tend to pull out at in-appropriate times like when big fish are hooked. I tried them once when I first started fly fishing back in the early 1970's. I use a loop to loop or a nail knot to attach my leader to the fly line.
The tool Ard was refering to was probably the tie-fast knot tying tool. Which is helpful but not essential for tying nail knots.
You can see one here at Cabelas
Cabela's Online Store - Quality Hunting, Fishing, Camping and Outdoor Gear
Regards,
Tim C.