This makes a nice cushion under the 20 mil vapor barrier we bought. I first tried to cut it with a box cutter, but the box cutter couldn't puncture the material. Then I got out a sharp pair of scissors and that worked great for cutting the pieces we needed. So, I think the felt will really protect vapor barrier from any sharp objects or stones. We pulled more than 50 rusty nails out of the dirt and I wanted to make sure that if we missed a nail we wouldn't have a hole in the vapor barrier.

worked great!

I like this product for the big peace of mind at modest cost. It's almost impossible to be 100% certain you got all the sharp, poky things out of the dirt but this felt takes care of that. Plus your knees will thank you when you forget your knee pads. The added thickness is a real plus and shows this company cares about quality and continual improvement. One last benefit: if you ever need to deal with radon gas, the felt makes a great air transfer layer u dear the vapor barrier.

We have recently used the 42 5100 under our 20 MIL liner and I will have to say it's a must. We will be using this product under our crawlspace liners from here on out.

1) GOOD: This is not like roofing "42" , and shouldn't be. 42 has an organic fiber base which will decay if continuously wet, as underneath a vapor barrier. This synthetic product is just what is needed as a vapor barrier underlayment. 2) OK: I got this to protect my vapor barrier from sharp-edged gravel which was already covering my crawlspace floor. As such, this product is OK, but not as thick as I expected. It is like an extra-thick landscape fabric.