Checking the Use simulation check box opens the Simulation Transform
socket in the template and allows you to drag a simulation transform
puzzle piece to that socket. If the Use simulation check box is not
checked, the simulation portion of the template is hidden.

Gamut Alarm

Gamut alarm causes any prints made with a color connector file to print
only the portions of the image that are out of the gamut of the selected
source or destination transform. The choices are “Off ”, “Simulation”, and
“Destination”.

When you select “Simulation” or “Destination”, the puzzle piece for a
simulation or destination transform is black indicating that you are using
Gamut alarm. If the Use simulation checkbox is not checked, Use
simulation is not available.