How are these seats meant to be bolted into the car?

I bought some from Exeter last year on special offer and they were put straight into the loft in plastic bags as I wasn't ready to fit them at the time. Just dragged them out and I was expecting for there to be some threaded mounting bosses on the bottom, but the only thing I can find is the end of a few pop rivets sticking out from the vinyl on the base of the seat. Have felt though the vinyl to see if there are any holes that have been covered up but nothing obvious.

If you lift the base of the seat forwards, you get to the fibreglass base. You have to drill your own holes to suit your own application. Use big penny washers to spread the load.

I used large penny washers and trimmed one side off them so that I could get the bolts closer to the edges.

my seats are like that, not sure if the same make butt he seat base is fixed with material to the frotn - you lift up at the read and it is held down with velcro.

I used four 8 mm coach bolts as these have heads the protrude less than hex heads - buttion head (dome shape with allen key socket are better but aren;t available in the longer lengths).

If you need to raise them a bit so they clear the chassis rails, get down to B&Q and get some 20 mm squere ali.

Thanks chaps, knew I must have been missing something obvious!