Lock was born on the planet Kamino, as one of the thousands of clones of Jango Fett. He served as a Captain in The Grand Army of the Republic in the Clone Wars. In 21 BBY, Lock was aboard a Venator-Class Star Destroyer called the Steadfast with his commander Eeth Koth on a patrol, when three Munificent-Class Star Frigates and a Separatist destroyer led by General Grievous attacked them near the Arda System. Eventually, the Steadfast was forced into submission. Lock and his troops attempted to prevent the Separatists from boarding. Koth was able to contact him, and he told him to board escape pods and retreat. Lock objected, but obeyed.