I never thought to look there but you are spot on in as much as you can see from the footwell what is going on. There is a wooden frame and it looks like that is where the bolts are. Someone has inserted a metal spacer too presumably to stop any distortion when the bolts have been tightened.
![[Linked Image]](https://www.tm-img.com/images/2023/03/28/IMG_4619-1.jpeg)
