Besides energy shields Ablative armor protects ships when equipped with it. With shields down a vessel can still take many hits until a weak spot is formed and compromised, similar to the old Ironclads.
https://memory-alpha.fandom.com/wiki/Ablative_armor
This, of course, is a technology in the TNG/DS9+ era and this thread is about the TOS Enterprise tech level.
Not sure if it was in a tech manual or story but I remember reading about a special shield system, TOS or TMP era. A block of neutronium is scanned then replicated/beamed outside the ship to intercept enemy weapons fire. The result is a projected section of impenetrable hull material to protect the ship from attack. Probably has limitations due to power needed and number of attacking vectors but an interesting concept.