Step 1: Loosen the knot in the middle.

Step 2: Move one of the washers close to the hole on the backside of the stick.

Step 3: Grab both strings on the back of the stick and pull until the knot comes through the middle hole and two loops are left protruding. 

Step 4: Slip the washer through both of the loops. 

Step 5: Again, pull the knot, through the hole in the middle, to the original side of the stick, and the washer will slip into place.