Which of the following is used to secure box rib lagging to equipment?

• A. 1/4 in self tapping screws
• B. 3/8 in self tapping screws
• C. 1/2 in self tapping screws
• D. 1/8 in self tapping screws

Answer: (B)

When securing box rib lagging to equipment, you need a fastener that can bite into metal and provide solid holding power without causing damage. A three-eighths inch self-tapping screw offers enough diameter to grip the metal and enough shear strength to keep the lagging in place during vibration and temperature changes. Smaller diameters would likely loosen or pull out, while a half-inch screw could be unnecessarily large and harder to install without distorting the rib. So the three-eighths inch self-tapping screw is the appropriate, practical choice for this task.