  The subject of mechanical metamaterials has been gaining significant
attention, however, their widespread application is still halted. Such
materials are usually considered as stand-alone, vis-\`a-vis all characteristic
length scales being associated solely with geometry of material itself. In this
work we propose novel application of mechanical metamaterials as interface
regions joining two materials with potential of replacing bulk adhesives. This
idea leads into paradigm shifts for both metamaterials and adhesive joints. In
specific, we outline methodology for testing and evaluating confined lattice
materials within fracture mechanics framework. The theoretical and numerical
approaches are inter-winded, revealing a set of critical parameters that needs
to be considered during design process. Lattices that are stretching and
bending dominated are explored and failure maps are proposed, indicating
susceptibility to a certain failure mode depending on level of confinement and
characteristic dimension of each lattice's unit cells.
