Heat shield fixings

[Tigdlo]

I have to remove some of the exhaust heat shields in order to replace the offside rear brake pipe.
Do the fixings unscrew, or are they pushed onto the studs? They appear to be in good condition, so I would prefer not to destroy them!

 

[Wild E. Coyote]

They are bit of both. They should unscrew, but thread might be so corroded that it dissapeared

 

[Tigdlo]

Thank you! I will make yet another special tool to unscrew them.