The pipe end rule tells the pipes that come into a structure where they connect to that structure. Out of the box dictates that they connect at the center line of the structure. However, in the real world, that doesn't happen - the pipes are built, roughly, to the inside wall of a structure. So, you have the option to tell the pipes, through the pipe end rule, to end at either the inside structure wall, or the outside wall...and you also have an additional option to add whatever offset you want to THAT, to allow, say 3 more inches of penetration into the structure.
However, C3D has the limitation of connecting only one pipe from structure to structure...that's just how it is. I've seen folks create the pipes and then draw over them manually with a double pipe, so it at least shows correct graphically. It's a shortcoming, one among many...
I've not experimented enough with the part builder to know if you can create a double pipe as a part...anyone know?
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