How to Check a Taper Using a Ball

Using a marble or ball to check taper on a car is an traditional bodyman's trick.

Checking taper with a ball or a marble is a method used by technicians in the automotive collision industry to determine whether the panel gaps on the trunk lid and hood of the car are aligned correctly with their adjacent panels. If the alignment is correct, the marble will remain in the gap, rolling smoothly until it is caught at the bottom of the panel. If the marble rolls off of the gap, then the hood or trunk panels must be adjusted to fit correctly.

Instructions

1. Position the vehicle on a flat, level surface.

2. Hold the marble or ball at the uppermost corner of the panel gap and place your hand at the bottom of the gap.

3. Release the ball or marble and watch its trajectory as it travels down the panel gap. It should remain on a straight path all the way to your hand. If you notice it pulling one way or the other, the taper between the two panels is incorrect.

4. Align the panels with the panel adjusters underneath the hood or trunk lid. When this is done, close the panel again and test the taper with the same technique. Repeat until the panel is correctly aligned and the ball rolls straight down the gap between the two panels.

References

• "The Complete Guide to Auto Body Repair"; Dennis Parks; 2008