The classic nīpuʻu style lei is made by knotting the petioles of individual leaves together, as in this lei lau kukui.
Here, you can see the same technique used to make a lei lau hau.
A more frequently seen lei which uses the nīpuʻu technique is the lei maile. This lei has been untwisted a little to show the tidy knots which hold the lei together.