Wrapping is made by alternatevely tying Vertical HH (not DHH!) going left to right and right to left. The AC stays the same, the WC stays the same. Hands change their roles.
For training mount one cord of a convenient length on the AC (Lessons 1 and 2) with simple LH.
We shall take the right cord as a new AC. The left cord will be the new WC. Pull down the AC with your left hand and hold it under tension. With your right hand take the WC under the AC and make one loop as for the Vertical DHH going left to right (Lesson 4(1)).
Still holding the AC under tension tighten the loop, pulling the WC upwards to the right. Move the knot closer to the previous row.
Change your hands. Take the same AC with you right hand, pull it down. Take the same AC with your left hand and take it under the AC.
Make one loop as for the Vertical DHH going right to left (Lesson 4(2)).
Holding the AC under tension, tighten the loop. Pull the WC upwards to the left, moving the loop closer to the previous one.
For the next loop change hands again. Take the AC with your left hand and pull it down. With your right hand take the WC, take it under the WC, make one a loop as for Vertical DHH going left to right. Tighten the loop.
Go on knotting changing hands but not cords! Tighten your loops evenly and move them close together. To make your back-side look even try to slightely “over-tighten” each loop to put it directly under the previous one.