The PolyHatchet tools are designed to slice a mesh at the origin, remove half of the mesh and mirror over the side of your choice. It's similar to Mirror and Weld in ZBrush.
These tools are free to artists that have purchased the Hatchet Collection for MODO. If you own this Kit, this new kit is available to you free of charge and can be downloaded from your Gum Road Account.
Note: The Default Shortcut for the pie menu is Ctrl+Shift+C