ɪn nˈaɪntiːnhˈʌndɹɪd fˈɪfti sˈɛvən, pˈiːɾɜːsən ˈædᵻd ɐn ˈiːziɹᵻlˈiːs tɹˈɪɡɚ tə ðə dɪzˈaɪn, kɹiːˈeɪɾɪŋ ðə mˈɑːdɚn lˈɑːkɪŋ plˈaɪɚz dɪzˈaɪn.
In 1957, Petersen added an easy-release trigger to the design, creating the modern locking pliers design.