The labourer, Sunil Bawre (26), was sleeping in his hutment on May 15 night in Kundekata village near the construction site when a group of armed Naxalites stormed his house.
The ultras threatened the labourer with dire consequences if work was resumed on the road and bridge, police said.
Before nailing him to the bridge, they stuffed his mouth with a piece of bamboo.
Sunil, who was bleeding, was rescued by a contractor seven hours later yesterday morning, police added.