When dropping a ball under a rule that requires you to measure one or two club lengths take the cover off the club – usually a driver – so that there is no risk of dropping in a wrong place. If you do not remove the cover then you may measure too great an area in which to drop and the ball may first strike the ground in this additional area you have given yourself! If you play from a wrong place there is a 2 stroke penalty in stroke play and loss of hole in match play. The advice is to always remove the cover before dropping a ball. At any time, if you think you have incorrectly substituted a ball or incorrectly dropped or placed a ball in a wrong place and have not yet played it, you may lift the ball and then proceed correctly without penalty.
Rule 20 Lifting, Dropping and Placing; Playing from a Wrong Place