how you attach them is up to you. Saris makes a bar to mount them on but I used a piece of ply-wood, 4 brass bolts, and a few nails to make a platform to mount two bikes head to toe - see pictures

You need a Saris track to mount the bracket to. The track is then bolted to your vehicle.

depends what vehicle, mine is a van you could bolt it to the floor, bulk head anywhere.
I used 2x 6mm cap head bolts and put a washer and 6mm nut on the other side of the bulk head, it really is that easy.

A simple frame with foam padding is secured to the rear of a vehicle by six straps with plastic coated hooks (2 top, 2 middle and 2 bottom). On our hatchback all 6 straps are hooked onto the rear hatch and it easily holds our 3 bikes. You must ensure that the car is clean otherwise the dust/dirt WILL mark the paintwork - we have not had any problems with this rack at all.

It fits all my mountainbike forks. have not tried my commuter or an other bike. But it looks they all fit.

Fits my kids BMX bikes, my mountain bike & my 700c road racer.

These fit all 3 of my bikes. Racer, hybrid and mountain bike with no problem