Mechanical assembly for securing sheets and related method

A mechanical assembly for securing a first sheet to a second sheet, the mechanical assembly comprising:

• a first projection extending from a first base wall of the first sheet, the first projection including a first sidewall, a first internal space and a first top wall, the first sidewall extending from the first base wall at a second acute angle, a first discontinuity defined in the first sidewall between the first top wall and the first base wall, wherein the first sidewall extends at a first taper away from the first internal space between the first top wall and the first discontinuity and extends at a second taper away from the first internal space between the first discontinuity and the first base wall, the second taper being greater than the first taper;
• and
• a second projection extending from a second base wall of the second sheet, the second projection including a second sidewall and a second top wall, the second sidewall extending from the second base wall at a fourth acute angle, a second discontinuity defined in the second sidewall between the second top wall and the second base wall, the second projection nestable in the projection in a nested configuration with the first discontinuity positioned proximate the second discontinuity that is configured to cause predictable failure of the first and second projections during assembly of the first and second sheets.