un·der·lay 1 
(ŭn′dər-lā)
(ŭn′dər-lā)tr.v. un·der·laid (-lād), un·der·lay·ing, un·der·lays
1. To put (one thing) under another.
2. To provide with a base or support.
3. Printing To raise or support (the level of a bed) by inserting a piece of paper or other material under the type.
n. (ŭndər-lā′)
1. Something, such as felt under a carpet, that is underlaid. Also called underlayment.
2. Printing Paper or other material used to underlay.