A door module of a vehicle includes: a panel of door glass including an upper peripheral edge and a lower peripheral edge; a lift plate coupled to the lower peripheral edge of the door glass such that a regulator may move the door glass between a full-up position and a full-down position within the door module via the lift plate; and a position block movable within the door module to: (i) a first position below the lift plate such that the lift plate rests on the position block and the door glass is at a position above the full-down position when the door glass is inserted into the lift plate during manufacture, and (ii) after such insertion, a second position that permits the lift plate to move further downward such that the door glass is at the full-down position.