Flip guards are components that are usually attached to switches that are critical in some regard. They provide a plastic cover that requires an extra step of the user for them to engage or disengage the switch. These are commonly used in scenarios where there is some sort of safety concern associated with changing the condition of the switch.
For example, if there is machinery that evacuates all the liquid from a line in the event of an emergency and that machinery is engaged via a modular switch, a flip guard might be positioned over that switch to prevent accidental usage. These flip guards are very effective in that, not only do they prevent someone from accidentally flipping a switch that they should not, they also prevent someone from being able to flip a switch without thinking about it first.