books provides confidence in the model. Furthermore, it is noteworthy that the classic phonebook T demonstration probes a broad range of loads, that typically consists of two decades, and a nearly sixfold chauge t in the coefficient of kinetic friction. The self-similar Eq. (3) suggests that with T" 0.01 N, and the best fit values of pu for each experiment a(see Fig. 3), all data should collapse when normalised appropriately. Indeed, in Fig. 4, we plot the rescaled total traction force as a function of the amplification parame- ter, and observe a single master curve for all experiments, with varying d and N The tremendous geometrical amplification of friction through the interleaving of the 2M sheets of each book bears a resemblance to two everyday examples. First, a