Transporting a mattress does not have to be a complicated process. The most important things to keep in mind are that you cannot block the driver's forward view, and the mattress must be fastened securely enough that the wind cannot blow it off the car. Also keep your speed as slow as possible during the moving, as non-reinforced mattresses can be damaged by high wind speeds.
Place the mattress on top of the car. Position it so that it is centered from side to side and flush with the front of the vehicle.
Tie the rope to the left rear bumper support. If you cannot tie directly to the bumper, loop the end of the rope over a sturdy brace beneath the car. Look for braces placed on both sides of the vehicle to give you balanced positions for placing the rope.
Extend the rope over the top of the mattress to the front of the car. Stretch it to the right front and loop it around the front bumper support beneath the car. As before, if you can't access the bumper support, find the right-hand side of a pair of brackets to use instead. Be careful not to place the rope on or over moving parts of the vehicle. Pull the rope tight, and tie it to the support.
Pull the rope beneath the front of the car to the left side, and loop it over the matching support bracket. Pull the rope over the front of the bumper and back across the top of the mattress to the right rear of the vehicle. The rope should form an X across the top of the mattress.
Wrap the end of the rope over the support or bracket that matches the one used on the left side, and pull it tight. Tie the rope to that location while keeping it tight over the mattress.
Open the car windows, and pull the end of the rope through the right rear window. Run the rope through the car, out the left rear window and over the top of the mattress. Wrap the rope around the mattress and roof of the the vehicle twice, and tie the rope to the column between the front and rear window. Stow the remaining rope inside the cab of the vehicle.
Tie red flagging to the rope on both sides of the rear of the mattress. Make sure that the flag can move freely in the wind as you drive. This flagging is to alert other drivers of items that hang beyond the length or width of the vehicle and is required by law in most states.