The Juxtaposition Cross of Depth is named for Gate 48 and Gate 21. Human Design reads Gate 48, from Hexagram 48, The Well, as a well of instinctive knowledge not yet made useful, elsewhere paired with Gate 16 in the channel of the Wavelength, and Gate 21, from Hexagram 21, Biting Through, as the will to control material life and the resources one calls one's own, paired with Gate 45 in the channel of Money. Juxtaposition Crosses stand apart from the other two families, tied only to the four line one profile, and are read as the most fixed direction the system names.
Its design half is Gate 53 and Gate 54, both in the Root. Gate 53 is read as the pressure to begin, an impulse that starts new cycles and often has no interest in seeing them through; elsewhere it pairs with Gate 42 in the channel of Maturation. Gate 54 is read as ambition, the drive to rise and transform one's material circumstances; it pairs with Gate 32 in the channel of Transformation.
So a chart carrying this cross holds an untapped well of instinct beside a will to control what is one's own, while beneath both a Root pair of beginning and ambition drives what the surface has not yet made useful. The hexagrams are ancient; grouping them into one incarnation cross is the modern system's own construction.