[Gmsh] Is there any "special magic" to Extrude?

[wibr]

Hi,

I am currently in the process of rewriting a tool to create geometries 
in form of .geo files. The previous tool was not written by me.

For creating the geometry for 2D meshes it will just create a list of 
points, lines and a surface which will then be extruded. So far no problem.
However for 3D meshes after this exact same process all the connecting 
lines/surfaces between the original surface and the extruded one are 
deleted and then recreated (otherwise the meshing won't produce the 
desired result).
This seems rather inelegant to me. I would very much prefer to create 
the extruded part on my own, since deleting the items requires the 
numbers of those, which are determined from example geometries and must 
be hard coded, therefore the whole thing becomes really error-prone.

So, is there anything what the Extrude command does which can't be done 
manually using the basic elements and commands like Point/Line/Surface 
and Translate/Rotate?

Thanks!
Wilhelm Brasch