For holding, through grommets, reverb tank to steel chassis, so not the
usual small ones for DSP boards etc. You cannot reinsert, blind, as the
4 splay bits are permanently splayed out.
Find a metal plate with holes the size to push each rivet in, to close
back the 4 splays, then old soldering iron and hotmelt glue the 4 together.
Reinsert through grommets and chassis, then the closer rivet, with more
force than usual to break the hotmelt .