Where is the mark for a penalty tap?

• The referee must indicate the mark before a penalty tap is taken, and the tap must be taken without delay after the mark is indicated (delay is a penalty to the non-offending team at the point of infringement).
• Infringements between the seven metre lines: the mark is the point of infringement unless the referee indicates otherwise.
• Infringements within the seven metre zone: the tap is taken at the nearest seven metre line.
• Infringements beyond the field of play or in the in-goal area: the mark is seven metres infield from the sideline, directly forward of the infringement on the nearest seven metre line, or a position the referee indicates.
• The tap must follow the definition: ball on the ground at or behind the mark, both hands released, gently tapped with either foot (or foot touched on the ball), moving no more than one metre and retrieved cleanly. Otherwise the referee instructs the team to return to the mark and tap again.
• A player may perform a rollball instead of a penalty tap, and the player receiving the ball does not become the half.
• Defenders at a penalty tap must retire ten metres from the mark or to the defending try line.

Source: FIT Playing Rules 5th Edition, definitions and rules 15.2 and 18.