…Then comes the sound of metal on metal.
The problem is the mower deck is deformed and bent. The older and more mangled a mower gets, in my experience, the easier this happens.
Assuming the blade has not been bent (if it has, you need a new one; don’t even bother trying to bend it back straight) here’s the fix I use. It’s usually easy.
Click below to read more from Mark on DIY Network.