Nejime is a securing tie used to hold warp threads together. It is recommended to make Nejime and other securing ties from thin cotton thread because cotton makes a more secure knot than synthetic threads. Tie a square knot at one end of the warped threads, move along the fiber  warp bundle,  ½ inch to ¾ inch, tie another square knot.  Pass the chopstick through the loop just created, insert chopstick through hole in mirror, pull chopstick and thread bundle flat under the mirror.

Picture of the nejime from the bottom of the mirror.