1. 
   Underlayment
   A material placed under finish coverings, such as flooring, or shingles, to provide a smooth, even surface for applying the finish.
   Found op http://www.rookinspections.com/glossary/glossaryu.shtml
   
   
2. 
   Underlayment
     Asphalt saturated felt used beneath roofing to provide additional protection for the deck.
   Found op http://www.pmel.org/Roofing-Glossary.htm
   
   
3. 
   underlayment
   1) Carpet pad 2) Pad 3) Rug pad 4) Underlay
   Found op http://www.mijnwoordenboek.nl/EN/crossword-dictionary/underlayment/1
   
   
4. 
   Underlayment-
   A ¼' material placed over the subfloor plywood sheeting and under finish coverings, such as vinyl flooring, to provide a smooth, even surface. Also a secondary roofing layer that is waterproof or water-resistant, installed on the roof deck and beneath shingles or other roof-finishing layer.
   Found op http://www.homebuildingmanual.com/Glossary.htm
   
   

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