Rule 6.3D

When Player May Play More Than One Ball at a Time

A player may play more than one ball at a time on a hole only when:

• Playing a provisional ball (which will either become the ball in play or be abandoned, as provided in Rule 18.3c), or
• Playing two balls in stroke play to correct a possible serious breach in playing from a wrong place (see Rule 14.7b) or when uncertain about the right procedure to use (see Rule20.1c(3)).