noun
ditch cover boards; boards over a drainage ditch
Refers to the wooden or metal planks placed over open gutters or drainage ditches, often seen in older urban areas.
路地のドブ板が外れて危なかった。
The ditch cover board in the alley had come off and was dangerous.
noun-modifying (irregular)
grassroots; door-to-door; on-the-ground
Used prenominally in political or campaign contexts to describe activities that involve direct, person-to-person contact, like canvassing or local organizing. Often in phrases like ドブ板選挙 (grassroots election campaign) or ドブ板活動 (door-to-door activities).
彼はドブ板選挙で支持を広げた。
He expanded his support through a grassroots, door-to-door campaign.
ドブ板活動が地方選ではまだ重要だ。
Door-to-door activities are still important in local elections.
草の根 also means 'grassroots', but is a more general term for bottom-up movements, not specifically tied to door-to-door campaigning like ドブ板.
Compound of ドブ (ditch, gutter) and 板 (board, plank). The literal meaning 'ditch cover boards' gave rise to the figurative political sense, likening door-to-door campaigning to walking over the boards that cover gutters in neighborhoods.