Figure 3.27 - Auto Merge option
With Auto Merge enabled, you can set the minimum distance used for
merging polygon elements. The default distance (0.001) will make sure
you have only vertices sharing the same location receiving an Auto
Merge. Leave Auto Merge enabled to make Blender remove all those
vertices without pressing the M key or the Context Menu.
3.7 Using the Mirror tool for modeling
A large number of objects that are subject to a 3D modeling in Blender
will present some kind of symmetry. Working with any object with a