a printhead assembly including a printhead module and a mounting structure is described . the printhead module is mounted on a receiving surface of the mounting structure and includes a first edge and a second edge opposite the first edge . the first and second edges extend beyond edges of the receiving surface by a first distance in a first direction and are positioned between featured edges of the mounting structure in a second direction that is substantially perpendicular to the first direction . each featured edge includes a first feature protruding from the featured edge by a second distance in the first direction , where the second distance is greater than the first distance . the first features extend beyond the first and second edges of the printhead module . each featured edge includes a recessed second feature configured to receive a first feature of a neighboring mounting structure .