Does anyone know what these parts are called?

There are 6 of them, 3 to the left of the drive shaft and 3 to the right. Two on each side are inside the frame rail, and one is outside the frame rail. They are located in the floorboard (2002 Xtra Cab) very close to the rear of the cab.

I’d call them drain plugs, but I cannot find them listed on a parts diagram, nor can Toyota. Has anyone replaced these? If so, can you provide guidance on how to do it?
Thanks

 

That's probably what your seats bolt to or something in the cab. Don't think they are drains. The have bolt coming threw

 

This^

 

yep, they are seat washers with welded nuts on them. helps spread the load of the bolt.