To tie on a reel:
1. Wrap the line around the spool and then tie a half hitch around the main line.
2. You are tying a half hitch with the tag end itself, the mainline just happens to be through it. So the mainline is not included in the half hitch per se.
3. Tie another half hitch to the very end of the line.
4. Pull the half hitch around the main line tight and slide it down on the spool.
5. Pull the main line until the half hitch at the end of the line jams up against the other half hitch.
6. Pull it just enough where the line starts to stretch, then release and it should be locked on the spool.
To tie on a filler spool:
Grab the tag end of line on the spool. With your other hand run a finger under the line still on the spool and follow it around until you’re back around to the tag end. Now pass the tag end under and tie a half hitch with just the tag end around the main line. Pull the knot tight. Now grab the tag end and pull it tight as you rotate the spool. If you are rotating it the right way it will walk down the spool and the line will snug up.