Position the nut, then slide a flat blade screwdriver behind it, pressing towards the bolt. Thread the bolt, then wedge the nut in place until you're done.
If you follow this, try to avoid the screwdiver to touch the frame in case the negative terminal is already connected. ![Grin ;D](http://forums.sohc4.net/Smileys/default/grin.gif)
Make it a habbit when installing a battery to connect the positive terminal first and when removing to disconnect the negative first.
Thanks. You may have saved my life. I was wondering about this.
Anyway, actually, the real trick, for me at least was to lower the battery in there only about 90% the way down there(it's tight down there and it stops against something, for me at least) leaving some finger room to maneuver the nuts on without any extra makeshift instruments.