What is that black bolt in my amp?

[InsomniaClown]

I have a series 2 rectoverb. There is a black bolt in between my V4 tube and my power tubes that hangs out of the chassis, and doesn't seem to be connected to anything. It also loks like there is some rust or charring around where the bolt goes into the chassis. What is this supposed to do? Any help would be great!

 

[ellem52]

Look at the LSS Chassis bolt Sticky at the top of this forum

 

[InsomniaClown]

Thanks! I guess I should have checked on that first.