What you should use if you jack your car up from the side
 

To protect the side sill, you really should have something like this. I don't recommend wood as they can split easily, my friend ended up making it for me in trex

http://img130.imageshack.us/img130/4887/dsc2770m.jpg
Shot at 2010-04-04

nice! you can also just use a hockey puck with a similar cut. that's what i did.

I bought a pinch weld jack adapter before reading about using a hockey puck. The adapter looks like this:
Grip Pinchweld Jack Adapter

Hockey puck is cheaper and doesn't deform like how I initially feared it would. If you use a piece of wood, make sure you cut the groove across the grain (not with the grain). Also watch that the piece of wood doesn't compress (soft wood)...a piece of hardwood would be better.

Padded floor jack pad good enough so far,....
Free,..not many hockey pucks in Hawaii... :)

Yep, the hockey puck doesn't deform. It's pretty sturdy, more then I expected. I had wood crumble or break apart on me before.

That is synthetic wood, not really wood

There is a guy on G35 Driver who molded some jack pads for the factory jack location. I was thinking of getting some. You have to go a few pages but it's located here:

Jack Pads

one thing i noticed that the Z has less clearance on the inside vs my G35C so for me, i made a narrower pad by maybe 1cm on the inner side of the rail.

I don't get it? How do you use it? I just put my jack under some sturdy frame parts and jack it up. I only did it once so far for my fist oil change. Anyone willing to put up a pic of it in use?

Thanks Bob