What does “bolts” mean here?
I used to crouch down into the seat and hold my coat in front of my face when I sensed a frightening scene coming, peeking through the buttonhole to find out when it was over. Through the buttonhole Frankenstein’s monster glowered; lightning flashed; sweat poured over the bolts that held his face together.
From the short story “The Movie House” written by John Updike