yield sign

I have hit the yield sign all over with my rock and cannot break it. Can someone help me with where I have to hit it? I'm at a lost. Please help.

I don't know if it will help but whenever I had a problem finding the right place to attach, stick or hit something in this game, I moved my mouse around until the pointer changed to the gears icon. If it was the question mark, I knew something needed to be done but not with the object I had grabbed. No change to the pointer meant I needed to continue looking.

if u go under the car (sparkles) u can detach the sign with the stone that way. hope it helps. took me 2 day to figure it out