I'm installing 1/4" underlayment in my bathroom. The book I have shows to screw the sheets down, and screw the screws in until they're just below the surface (so I can level it and have a smooth surface for my new flooring). The problem is that the screws will screw TO the surface, but then they just spin in place. I can't get them to go in tight enough to pull the heads below the surface of the underlayment. I'm using 2 1/2" screws... I was using shorter screws, and thought the longer would do the trick. I was wrong about that. A guy at the hardware store said to locate the joists and screw into those, but I need to put screws every 6" around the edge of each sheet and across the area of the underlayment every 8"... I doubt the joists will help me with those spots.

I was at a job site about a year ago and noticed a box of 20d ring-shanked nails lying about and am wondering what a typical application for these large nails is! It would seem that whatever is being nailed together, you'd pretty much need to be sure where you tied it together because the nails would be a real bear to pull back out!