mccsix

Can anyone tell me where I can buy or borrow the skinny little tool that you need to reset the front headrests on my '07 CLK350?
Also there is conflicting info on whether you need to locate the "channel" on the left side of the HD to insert the tool OR whether you insert the tool in the small fitting center hole to make the necessary adjustment.
My car didn't come with the too so I have no idea size shape dimensions etc to make my own. If anyone can provide the info I would sure appreciate it.
Gene