forming tool 24 a having a base sidewall 29 a defining a generally quadrilateral perimeter and a plurality of sidewalls 31 a extending transversely from the quadrilateral perimeter in order to define a cavity 33 a having an opening 35 a that opens in a second direction as shown in fig2 a and 3a the first forming tool may be a male type mold structure 24 or a female type mold structure 24 a a first material sheet 20 fig3 a is plastically deformed through heating the first material sheet 20 a which allows the first material sheet 20 a to form a first intermediate structure 30 a utilizing the first forming tool 24 a edges of the first material sheet 20 a are clamped to flanges 28 a or transversely extending sidewalls 31 a by clamp 21 a in order to form the first intermediate structure 30 a once the first intermediate structure 30 a is formed it typically comprises a base sidewall 32 a defining a generally quadrilateral perimeter 34 a and a plurality of sidewalls 36 a extending transversely from the quadrilateral perimeter 34 a in order to define a cavity 38 a having an opening 40 a that opens in the second direction next a second forming tool 50 a fig3 c is disposed inside of the cavity 38 a of the first intermediate structure 30 a the second forming tool 50 a typically has sidewall portions 52 a defining a plurality of generally rectangular outwardly facing surfaces 54 a and inwardly facing surfaces 56 a and at least one end surface 58 a extending transversely between the inwardly facing surfaces 56 a and outwardly facing surfaces 54 a moreover the second forming tool 50 a includes a cavity 57 a defined by.