"Let's model me a mine"
M.E.G.M.S.
Mining & Exploration Geological Modelling Services
Merge command (Tools menu and Toolbar) 
Select this command to select the Merge tool. When using the Merge tool
the mouse cursor changes to a "merging" unit (
) and "Merge" is displayed in the MEGS_Log
status bar.
With the Merge tool you can left click on a unit to expand it upwards to occupy the space of the unit above (the unit above is deleted).
The Merge tool is not affected by the current Insert Mode.
The shortcut key for this command is F5. You can cancel the Merge tool and return to Normal mode by pressing the Escape key.
See About Editing Tools for more information.