Crossword Puzzle Thin boards under your mattress

Clue: Thin boards under your mattress

Things understood by few (ARCANA with 6 letters)
Thin mattresses (FUTONS with 6 letters)
Thin mattress (FUTON with 5 letters)
Understand how things are done (KNOWTHEROPES with 12 letters)
Thin boards (SLATS with 5 letters)
Things are easier to understand on his terms (LAYMAN with 6 letters)
"I didn't understand a thing you said" (THATSGREEKTOME with 14 letters)
Underneath (BELOW with 5 letters)
The real thing (FACT with 4 letters)
"There's no such thing as a dress that's too small" (THEMONROEDOCTRINE with 17 letters)