I got the following Schumacher battery charger/maintainer for my 2002 IS300:
Schumacher Electric Schumacher Pro Automotive 6-Volt/12-Volt 2-Amp Battery Charger and Maintainer with Auto Voltage Detection SPR1627 - The Home Depot

The instructions say to not connect the negative clamp to the negative battery terminal, but rather to ground on the engine block. However, the negative clamp doesn't reach that far. I found a random bolt that reaches, but I'm reluctant to connect it to something that I don't know what it does. Is there any risk of damaging a component by connecting it in the wrong place?

 

You can clamp it to the battery. Been doing it for years.

 

I wonder why it says that

 

If the battery is bad and you charge it. It will give off a flammable gas. Some when the battery is good also. If it is a well vented rea. Does not matter. Also making sure there is no arcing from the cables.