Door & Button/Lift Hiders
From Creatures Wikia
The Button, Door and Lift Hiders are actually two separate agents. The Door Hider only works on doors, while the Button/Lift Hider works either on call buttons or elevators. As the name says, these machines lock their associated agent type by making them invisible to creatures. Doors, Buttons and Lifts can still be activated by the Hand at any time.
When first injected, the Hider shows a roving red button/light. When placed over an agent that it can lock, the button stops moving and remains in the center. When clicked, it turns blue, indicating the agent it is touching is now invisible to creatures. All of the Hiders float and can be easily positioned over any button, door or lift. Door Hiders are light blue, while Button/Lift Hiders are tan colored.