There are three parts to a pleat. Let's say that we have a kilt that is pleated to the stripe to make my explaination easier. So, lets look at one pleat. A pleat is shaped in a Z. The top of the Z is the stripe. The bottom of the Z is actually the next pleat. It is my hypothesis that the middle section of the Z is the leaf spring. It will bend when pulled on by the upper and lower legs of the Z. With 29 pleats, each pleat will only have to open 0.2" to have a total 6" swing of the outside pleat.