Change vertex selection using pick walk

User Guide > Modeling > Polygonal Modeling > Polygon selection and creation > Polygon selection >

You can use the arrow keys (uparrow, downarrow, left arrow, right arrow) to change the selection of vertices in a polygonal mesh. This is useful when you need to quickly change the selection to neighboring vertices when modifying a mesh.

To select and then walk a selected vertex or selection of vertices across a mesh

Select a vertex or group of vertices on a mesh.
Single click using the left, right, up, or down arrow keys to walk the selection in any direction along the mesh.

The following limitations exist on vertex selection with arrow keys:

This feature works best when the selection is a single vertex.
When pressing an arrow key would select a vertex that is hidden (for example, on the back side of geometry), you will need to tumble the view to continue pick walking.
If you have multiple vertices selected and you pick walk past the visible portion of the object, the original selection will not be preserved.
You cannot always reverse the vertex selection in complex geometry; that is, if you press left-arrow to move a vertex selection, right-arrow will not always bring you back to the original vertex.
You cannot always get back to the initial selection state when you select multiple vertices and pick walk.