Chest panel

The chest panel was the front of the Cyberman chest unit, (TV: Silver Nemesis) covering the ventilator unit. (PROSE: Earthshock)

A Cyber-Controller which resided on Telos had a chest with no visible panel. (TV: The Tomb of the Cybermen) Later, its body was modified to more closely resemble that of the subordinate Cybermen. (TV: Attack of the Cybermen)

As a target
Lady Peinforte and Richard Maynarde used gold-tipped arrows to kill Cybermen by striking their chest panels. Likewise, Ace used a slingshot to fire gold coins at the Cybermen, with the Seventh Doctor instructing her to aim for their chest panels. The Cyber-Leader was able to survive a hit to its chest panel, removing a coin from its chest unit, only to be killed when Richard thrust a gold arrow into its chest unit. (TV: Silver Nemesis)

When exterminating Cybermen, Daleks such as the Cult of Skaro typically aimed at their chest panels. (TV: Doomsday)