Hi again!

Seems that they are talking about a shop window. Could be possibly refer to dummies, and the way you should arrange them there?. If it is the case, those dummies can be take to pieces, and should be put together in a certain way, which is what they are trying to explain there.
It's just a guess!.

first piece 'refers to first piece of bar". I hope the implied meaning is clear enough.

You did great on providing specific contents -- the whole sentence. And I think your answerers did admirably well in divining the general context. But it's generally a good idea to explicitly STATE the general context (e.g. plumbing vs. wiring :-) ) in addition to the specific context in KudoZ queries. That can often save us time, and gives you an even better chance at valid answers.

All the best, Tom

I still haven't grasped the situation fully. What are "face out bars"?
rods, racks, ...?

I think the first piece may be the first outfit from the viewer's point of view. But I still can't picture the setup.

If somebody actually understands this sentence it's worth writing it out.

what the text is actually referring to is those rails in clothes shops which stick out horizontally, perpendicular to the wall, and on which various items of clothing are displayed, on hangers.

The first piece means the first item of clothing (i.e. in this case on a rail full of blousons), the one at the front should be made to look more attractive by putting other items to clothing with it to create a whole 'look' or 'image'.