More A-class questions

More questions about the A-class.
1. Where to find the gadget to unlock the locked wheelnut on the wheels?
2. How to leave the car occupied, without the key in.
1. Unlock the wheelnut My tyre has a strange bulge. I will get it fixed, but want to fit the temporary replacement. I bought my car as an approved used model. There is a set of tools in the boot with the spare, but I can't see how to use them on the lockable wheelnut. Is the gadget stored somewhere else in the car or must it go to the MB garage to get the tyre replaced?
2. When the car as handed over, the salesman explained how to leave the car occupied witout the key in. I can't remember the details. The manual explains about the door, but what exactly is the trick with the light?
And out of curiosity, what is the long black bit of metal for, in the zip compartment at the front of the boot, at the back of the rear seat?
Thanks for previous info. I do lurk in /.
Also if this item looks odd, the let me know. I am trying out a new newsgroup reader/editor.
Regards, Sylvia
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