Every day you play the game, there's a rock that contains some hidden bells. You can whack the rock with a shovel to send some bells flying. Repeated hits during a limited time period will allow you to gain additional bells, but normally the number is limited somewhat by the step you automatically tack back after whacking the rock. One way to fix this is to stand against a rock, then dig holes to your left and right, as well as behind you. Now when you hit the rock, it won't send you flying backward. You can whack it more frequently to produce additional bells before the invisible timer expires, handily increasing your total earnings.