For each uniform structure, there also exists a related but different structure, called a line-slip arrangement.
The differences between uniform and line-slip structures are marginal and difficult to spot from images of the sphere packings. However, by comparing their rolled-out contact networks, one can spot that certain lines (which represent contacts) are missing.
All spheres in a uniform structure have the same number of contacts, but the number of contacts for spheres in a line slip may differ from sphere to sphere. For the example line slip in the image on the right side, some spheres count five and others six contacts. Thus a line slip structure is characterised by these gaps or loss of contacts.
Such a structure is termed line slip because the losses of contacts occur along a line in the rolled-out contact network. It was first identified by Picket et al., but not termed line slip.
The direction, in which the loss of contacts occur can be denoted in the phyllotactic notation , since each number represents one of the lattice vectors in the hexagonal lattice. This is usually indicated by a bold number.
By shearing the row of spheres below the loss of contact against a row above the loss of contact, one can regenerate two uniform structures related to this line slip. Thus, each line slip is related to two adjacent uniform structures, one at a higher and one at a lower diameter ratio .
Winkelmann et al. were the first to experimentally realise such a structure using soap bubbles in a system of deformable spheres.