Given the variety of types of advertising available on the outside of trams (see link), I would just avoid translating the word 'découpe' and just refer to 'the advertisement'.

I can imagine what it is, but I'm blest if I can think what it's called — I think it's one of those 'stick-on' plastic (etc.) things, a bit like a transfer, that is often profiled (think Paris skyline on the side of a tour bus) and stuck (more or less temporarily) onto the outside of the vehicle — more interesting than a simple geometrically-shaped 'poster'


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Note added at 49 mins (2007-10-10 10:43:04 GMT)
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Not really 'die-cut' Tamara, simply because I don't think they ever would be — the size is much toe large for a die, and also, the quantity produced too small to justify making the special die required.

I think these days they are produced by laser cutting, or by a computer-controlled 'knife'.