The Unit Weight of rock and water is specified in the Input Data dialog under the General tab.
The rock Unit Weight is always required for the Unwedge analysis, since the wedge self-weight is the primary driving force in the analysis.
The water Unit Weight will only be used in the analysis, if you are including Water Pressure on the joints, and you are using the Elevation option. See the Water Pressure topic for more information. If you are not using the Water Pressure (Elevation) option, then the Unit Weight of water entered in the Input Data dialog will have no effect on the analysis.
Note: the units used for the Unit Weight (i.e. metric or imperial) are determined by the setting of the Units option in Project Settings.