hole in carpet under driver seat, bolt through the floor

The car came back from having its stolen cat replaced a few days ago. Today when moving my junk back into it I noticed a hole cut in the carpet under the driver's seat. The flap of carpet is still there, with a few inches of insulation removed, and there is the head of a pretty substantial bolt, which goes through the floor. The bolt is close to the center of the seat and about four inches forward from the back end of the rails. I did have a cat shield installed while they were at it, but that doesn't extend back quite that far, and none of the connectors holding that are anywhere near that size.

I don't recall seeing that cut in the carpet before, but it is under the seat, so I could easily have missed it.

What is it for?

 

There is also one under the front passenger seat in the same position (measured from the front or midline of car.) It is posterior to the back edge of the shield and nowhere near the cat itself. The one on the driver's side seems to be above a white plastic conduit which runs front to back. It is roughly over what appears to be a square access plug (see attached). The one on the passenger side seems to over some black plastic. I don't feel the bottom of either screw, both seem to be under plastic. The bolts are 12mm. In both cases the carpet was cut, and a chunk of insulation removed, to expose the bolt.

If you press on the carpet in that area can you feel the head of the bolt?

 

The car did just have a cat shield installed but that is fastened on by small security head fasteners tips facing up, a few at the front, and a row on each side. The shield itself ends quite a way forwards of where these bolts are located.

On the other hand, the service department did replace the stolen catalytic converter at the same time. Perhaps these held on something on each side which needed to be dropped to put the new cat in? Seems a little odd, since they are not very close to the path of the exhaust system under the car.

 

Sorry for not being more specific. It is big, protruding, and a bolt, but yes, it is the head and not the tip.

 

I am waiting for a reply on that from the service department that replaced the cat and installed the cat shield.

If it wasn't them then there would be no way to find out. The car was bought used and all the previous work would have been either in the engine compartment or under the dashboard.

 

Nope, never figured it out.

It would probably work as a ground but better I think to ask that specifically in the "Gen 2 Prius Audio and Electronics" forum. Since it is far from both the dash perhaps best to measure resistance back to the negative post on the battery. Then do the same at some bolt under the dash. If the values are close it should work OK as a ground. If the bolt value is significantly higher, like >30 vs. 2 Ohms, perhaps there might be some issues.