At the right side of the bulb, user can set an icon which is a lock 
. If the lock is closed 
, the layer is frozen. If a layer is frozen, GiD won't apply anything to the entities of that layer, and its entities will be drawn in ligth gray color. For instance, if user select some entities to be deleted, if they are into a frozen layer they won't be erased.
GiD - The personal pre and post processor
General
Content
Integrations