Abstract: There is provided an improved apparatus for forming foldable box blanks from a thermoplastic sheet by forming flexible fold lines in the thermoplastic sheet, with the apparatus including a plurality of scoring tools and a flat plate having a plurality of grooves formed therein opposite to the scoring tools. In addition, the apparatus includes means for heating the scoring tools to less than the melting temperature of the thermoplastic sheet. In this manner, when the heated scoring tools engage the thermoplastic sheet, it is deformed on its upper surface by the scoring tools and on its lower surface by the grooves in the grooved plate to form a plastic sheet having the desired flexible fold lines.