What Was The Shuttle Bay In TOS In The Pilot Episode?

The transporter was depicted as the only mode of transport between a planet and the ship because this episode was written and filmed before the existence of the hangar deck and shuttlecraft were established, even though both of these locations are clearly built into the studio model of the Enterprise as seen in the episode. As the lack of a shuttlecraft was almost immediately pointed out as a plot error, production and writing staff later stated that perhaps the shuttlebay was simply out of service for repairs during this episode, which would explain why the crew did not use shuttles to rescue their comrades (Star Trek Compendium)