In addition to working with his brother, John Jefferies, to create the hand-held phaser weapons of Star Trek, Jefferies also developed the set design for the bridge of the Enterprise (which was based on an earlier design by Pato Guzman).
Pe lângă faptul că a lucrat cu fratele său, John Jefferies, pentru a crea fazerele, armele de mână din Star Trek, Jefferies a proiectat și puntea navei Enterprise (pe baza unui model anterior al lui Pato Guzman).