For Twins, Triples and Anchor Structures, without choosing which Equipment to attach to a Wire Point, Lineardraft doesn't know which wire should be assigned to which part of the Structure Symbol.
What happens when no equipment is assigned?
The image below shows a Twin Structure with two wires attached, one Equipment Line of the Structure Symbol extends past the dotted Out-of-Running Wire and the other doesn't quite extend to the solid In-Running Wire. In this scenario, no Brackets, SPS or Cantilevers have been assigned, and therefore Lineardraft doesn't know which wire to attach to which Equipment Line.
When there is equipment?
Once Equipment is assigned, Lineardraft knows which wire attaches with which Equipment Line (because you've told it!) and is able to adjust the Equipment Line lengths of the Structure Symbol to meet with the wire.
The image below shows the aligned Equipment Lines with a Twin Structure.
Stagger Symbols Assigning Equipment means that Lineardraft can determine the correct position of the Stagger Symbols too!