Crossword clue: a long thin board with one edge thicker than the other; used as siding by lapping one board over the board below

The most common answer is clapboard (9 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

clapboard 9 letters wn-def

a long thin board with one edge thicker than the other; used as siding by lapping one board over the board below

weatherboarding 15 letters wn-def

a long thin board with one edge thicker than the other; used as siding by lapping one board over the board below