Page 96 - Joseph B. Healy "The Pocket Guide to Fishing Knots"

Double Nail-Knot Loop

1. Use the Nail Knot to secure the heavier line or fly line into a loop.
Start by doubling over the heavier line. Tie a Nail Knot using a
needle or other straight object.
2. Here’s the first finished Nail Knot.
3. Now secure the loop with a second Nail Knot. Again, some anglers
coat the Nail Knots with super glue or silicone. Your call on that.