Add instances, not copies

About once a year, I start learning and modelling again. I fear that the following requirement is not possible:
Create 4 pieces of wood (4 objects), select them all, create a composed object (no, not join) and name it “bed”. The pieces’ relative position is now locked, so I can grab the bed as a whole and put it anywhere. I want to create multiple instances of this bed and place them whereever. The bed always looks the same. If I unlock the relative position (rotation etc) of the 4 pieces, I’m able to change the design of the bed. All instances still look the same.

You see the problem: I can’t create “a bed”. This level just does not exist. I mean a composed object with individual but glued objects. Isn’t this a basic task? Create a model and put several instances (not copies!) into the scence? If you change the model, all instances change their look because it’s the same model. I can’t imagine that you copy everything and have to do all changes for every copy again and again.

(Whenever I want to display the same object several times in D3D, I just change the transformation matrix between rendering the instances. I wouldn’t want to copy all object data. I also don’t see a kind of frame hierarchy in Blender.)

I must have missed something.

I’m not 100% on exactly what the problem is but:

Ctrl D = duplicate (copy not linked)
Alt D = linked duplicate (change one and all change)

Ctrl G = will create a group (but put your object(s) centre at the origin before you group it - otherwise it will be offset)
and then you can add as many instances of this group with Add> Group > name of group

you can also use the array modifier to create instances

hope this helps

Thanks.
I just wrote a lot to explain why this doesn’t work as required but fortunatelly I’ve seen my mistake :rolleyes:. So, yes, a group offers everything I need. Before, I thought Add -> group -> name of group just inserts a copy of the objects in the group, not the group as a whole. And I also first thought that we can’t group groups and objects to build superordinate groups. Luckily I was wrong. Just what I’ve been after.
Thanks again!