I use the same loop of dental floss to make both the top and bottom nocksets... it's just used as a "placeholder" in essence, though it does serve the function of pulling that tag end back through and under the wraps.

But I use two entirely different pieces of nock point tying thread for each nockset. They are two individual and different nocksets, just tied the exact same way save the number of wraps to complete each one... with those of course being four wraps to make the top one and eight wraps to make the bottom one.