Not the conceptual nature of doubling or the structure of a scene, but the actual literal mirror (and in general “reflective surface”), and this theme packs a punch.
From Danny talking to his own reflection as Tony, to seeing Jack talk to both Lloyd and Grady in front of a mirror, to the woman within Room 237 which shifts significantly from in and out of the mirrored reflection, and No.24 transitions not to Jack but to Jack’s reflection within the bedroom mirror.
We see the bathroom reflected in the mirror as Wendy paces back and forth, practicing her plan to escape —and we see how well that plays out during No.71’s Redrum sequence, again shown in a mirror.
The mirror is used by Kubrick to show layers of duality, reality, denial, and things looming.
Mirrors [Actual]
Image 158 "tony why don't you want to go to the hotel"
Image 321 "homey"
Image 408 "how'd you know we call him Doc?"
Image 777 [Jack walks down hallway to Gold Room]
Image 1061 same hallway as [Image 777/Image 901, but only 1 mirror is shown]
Image 1643 (fix pause symbol!)
In this image · No.6
Closing Day