You will need to find a bottle you like. I used an empty instant tea bottle, of course washed and dried. (I like to put the bottle in the oven for a few minutes to dry the inside without water spots. Take off the lid and do not put lid in the oven.) Now measure the circumference of the bottle. Take a cord and tightly wrap the cord around the bottle. Mark where the ends meet, and use a ruler to measure the length of the cord. For my instant tea bottle the circumference is 27cm. I know from past knots that I have tied, that I want my knot to have 20 Bights in the top and bottom (bands) knots. I am going to use the Bights in the (bands) knots to tie the middle knot. Now divide the number of Bights (20) into the size of the circumference (27) to get the space between each Bight (1.35)... With me so far???
Now take two pieces of painters tape, using a ruler measure out the length of the circumference and mark the length on the both pieces of tape. Next you will mark the space between each Bight on the tape.