A baffle plate or isolation plate was a component of warp cores, damage to which could be potentially catastrophic.
In 2266, Charlie Evans used his psychokinetic powers to remove a warped baffle plate on the survey vessel Antares, whose captain was attempting to warn the USS Enterprise of the danger that Charlie posed. Removing the baffle plate caused a warp core breach, destroying the ship with all hands lost. (TOS: "Charlie X")
During the same year, Fleet Captain Pike suffered severe radiation poisoning, and a number of cadets killed, when exposed to delta rays on board a Class J training vessel, due to a ruptured baffle plate. (TOS: "The Menagerie, Part I")
The Boslic cargo vessel commanded by Jaheel nearly experienced a collapse in its fuel cells in 2369, during an attempt to forcibly remove the ship from Deep Space 9's mooring clamps. His actions caused his ship's isolation plate to buckle causing the main power core to rupture, threatening a possible collapse of the internal fuel cells. (DS9: "Babel")