Abstract: In an apparatus for sealing the top flaps of a carton having a tape head assembly for applying a strip of self-adhesive sealing tape that extends along the upper portions of the leading and trailing end panels and across the top flaps, a tab forming device for forming a pull tab at a trailing end portion of the strip of sealing tape. The tab forming device includes a housing member having a cavity formed therein in facing relationship to the trailing end portion of the strip of sealing tape. A suction created in the cavity draws the trailing end portion thereinto so as to cause the adhesive surface of the trailing end portion to fold upon itself and form a pull tab. A means for controlling the dispensing of the tape from the roll is provided which includes a spool member which is biased into receiving contact with the outer portion of the roll.