Irons need a descending blow
Slide the toilet paper roll down the shaft and swing — for irons, the roll should reach the clubhead on the left side of the swing (post-impact), confirming your hands are forward and you are compressing the ball.
Driver timing is the opposite
Because the driver requires an ascending strike, the roll should travel to the clubhead on the right side of the swing, just before impact, which indicates you are creating lag and hitting up through the ball.
The sound tells the story
You do not need to watch yourself — the audible swoosh of the roll moving down the shaft gives instant feedback on whether your timing is correct for whichever club you are using.
