The unit is the base for an LED light chaser around an advertising
poster. The LEDs are mounted on foam board, which is very light
and no bother to hold up. The electronics have to be away from the
poster, but can't always be on the floor or hidden somewhere else

All of the suggestions are worth trying, and I could determine which
work better in different circumstances, such as DS tape in windows
that don't get direct sunlight, glues for more or less permanent
installations. Even combinations, such as suckers + small spots of
silicone. For the effect to be had, it's worth a little effort. I'll look
into any differences between plate and automotive glasses, perhaps
the superglues can be put to use in an auxilliary role, eg for the
foam board. And I was glad to be reminded of the bracket idea, which
came up once but I'd forgotten about. That would also make sense
with the poster - slip it into a pocket rather than dismantle the chaser

> 1.    You didn't say whether you are allowed a wire etc from the unit
> to eg power supply (it may have inbuilt power supply).

There's an external 5V supply, a thin black two-core. I tried a battery
+ solar panel but (a) a good crystalline one is too heavy/expensive and
(b) not many shop windows point upwards. None actually, so energy
collection is not good

The magnet idea is impractical for this window (I can imagine how
many of the outside ones would be left in the morning) but coincidentally
makes the best choice for another project I'm putting together that
can be framed - the magnets can go inside

I'll report back in a year or three