i think i know what you mean:
when creating a coaster, you need a straight section of a beam and a 45* section, for example. normally you use 3 nodes: the start of the straight section, the end of the 45* section and the connector node in the middle.
Now, as you ride that support in the sim, you'll see the it missing a piece of support in the shape of a pizza slice.
Right?
If you don't want this missing piece, you must use 4 nodes, the beginning of the straight section, the end of the straight section, the beginning of the 45* section and the end of the 45* section.
When normally both tubes end in the connector node, now the beams must extend a little longer so that you'll be forming an X like type. I don't know how much longer they need to extend, it depens on the angle and thickness.
I'm sorry i'm not on a pc with NL currently cause four pics can explain the previous story, anyway, hope this helps.