Lasso Knot

Step 1:

Form a loop.

Step 2:

Form a second small loop using the tag end.

Step 3:

Wind the tag end through the loop four times.

Step 4:

Lubricate, then draw the smaller loop down using the tag end to form the knot.

Step 5:

Trim the tag end.

Step 6:

Loop will now slide up and down as desired.