More details about the The Arbor Knot
Uses: The Arbor Knot is used to attach the fishing line to the "Arbor" or "Spool Center". In fact the Arbor Knot is really based on a noose knot and, therefore, pulling it tightens it.
Tying it: When the Arbor is accessible, the easiest way to tie the Arbor knot is create a Noose, drop it on the Arbor and pull it to tighten it. If you make a Slip Knot by mistake it will just pull undone. Alternatively, as shown in the animation, pass the tag end around the Arbor and use the end to tie an overhand knot around the line.
The overhand knot in the tag end is essential. As the knot is tightened it snugs down against the Arbor. Some fishermen recommend winding the loop twice round the Arbor before making the first half hitch. This increases the friction which may be useful on some of the more polished reels.
Advantages: The Arbor knot is simple, easily learned and effective.