underlay

Noun

• a pad placed under a carpet

Verb

• provide with a base, support, lining, or backing
  • underlay the boards with joists
    

• put (something) under or beneath
  • They underlaid the shingles with roofing paper
    

• raise or support (the level of printing) by inserting a piece of paper or cardboard under the type
  • underlay the plate
    

Related words

• Synonyms: 
  carpet pad , rug pad , underlayment