I've never done this job before, and a search didn't help. When I went under my parts car I noticed the inside bolt was not a standard 6 sided one but that one with many indentations, like a spline. What kind of special socket do I need to hold this bolt while ratcheting the outside bolt?

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)