What would you use when installing 3/4 inch thick under-layment?

Using 8d ring shanked nails when installing 3/4 inch thick underlayment is appropriate because these nails provide a strong hold while ensuring that the underlayment is properly secured without splitting the material. Ring shanked nails have small ridges along their shank that enhance grip and resistance to withdrawal, making them ideal for applications where a secure fastening is crucial, such as underlayment installation.

The thickness of the underlayment at 3/4 inch requires a nail length that adequately penetrates through the underlayment and into the subfloor while maintaining structural integrity. The 8d ring shanked nails, at a length of 2-1/2 inches, fulfill this requirement perfectly. They strike a balance between length and strength suitable for the task at hand.

Other options, such as 10d common, 12d finishing, and 16d framing nails, would not provide the optimal balance of grip and penetration for underlayment installation, either being too long or not designed for the specific needs of fastening underlayment materials securely.