What are those yellow lines on the outside of the mesh?

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:bust_in_silhouette: Asked By rogeriodec

Within this structure:

enter image description here

What those yellow lines mean?
And why they are outside my structure?

:bust_in_silhouette: Reply From: Calinou

These are gizmo helpers, which are only visible while the mesh is selected; they help you visualize the mesh’s boundaries. They won’t be visible when the project is running.

A small offset is applied from the actual mesh’s boundaries; otherwise, they could be hidden by parts of the mesh.