Bully,

>> What holds them in? <<

I think friction, at least at the start. When my sliding window end guides
started to slip I put a drop or two of Crazy Glue on them and just
reinserted them. Normally this worked fine. However in 1997 I noticed the
ends were seriously eroding away, probably due to sunlight and UV
radiation. I bought six new ones in 9/97 from the VW dealer: part number 281
847 723B @ $1.32 ea. These replacements are black plastic verses white on my
stock 83.5 GL. I had to trim a bit of excess internal plastic to make them
fit but it wasn't any big deal. I suppose there was a slight change between
1983 and the 1990's models. Also I don't recall whether I used glue on these
or not.

Garrett Adams
1983.5 Adventurewagen GL