Add an edge loop that runs across a specified section of a mesh
To create an offset partial edge loop
The Offset Edge Loop Tool options window appears.
A pair of edge loop preview locator lines appear on either side of, and parallel to, the edge you clicked. The green dotted preview locators indicate where the edge loops will be inserted across the mesh once you release the mouse button.
The Offset Edge Loop Tool selects any edges between the first and last edge you select and updates the edge loop preview locator as you proceed.
The new edge loops are inserted on the polygon faces associated with the original edge loop you selected. The original partial edge loop remains selected so that you can perform additional operations on it.
For example, selecting the Move Tool to move the selected edge loop, selecting Edit Mesh > Extrude to extrude the selected edge loop, or converting the edge loop selection to faces.
Depending on the extent of your edge selection, the Offset Edge Loop Tool inserts edges in a more radial fashion compared to the original mesh, based on how the Offset Edge Loop Tool maintains the four-sided topology when the Delete Edge option is turned on. This radial detail can be useful for creating features such as an eye, ear, or a mouth on a model of a character.