Actually I just remembered I did the 2 x 4 trick on a W124 and a W126. For the W210, due to more limited working space, the easiest redneck fix is to push the window all the way up, then use a small radiator hose clamp wrapped around the regulator track. Snug it up really tight to hold the window up and it won't go anywhere.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280