Cyclists are being warned after drawing pins were found scattered on a popular cycling route.
They were found scattered on the Bwlch mountain road, Rhondda, on Saturday.
Cyclist Paul Harries spotted them and warned others: "Stay safe everyone, someone targeting cyclists on the Bwlch descent down the Afan side. Just cleared a pile of tacs off the road."
He said that some of them were even painted black to make them more difficult to see on the road.
Another cyclist said it was a "common hotspot" for this type of thing to happen.
Earlier this month a dog walker on the mountain found blocks of wood with massive nails sticking out of them on the main trail.
They had been buried in the ground with the nail sticking up and left in a zig-zag pattern.
While Shaun Jones, of Rhondda , said he believed the intention of the people who planted the nails was to puncture tyres, it could have devastating consequences if they injured a person or an animal.
