What action should operators take according to the safety sticker regarding the emergency stop on a stacker?

Operators are advised to regularly test the emergency stop feature as outlined by the safety sticker. Regular testing ensures that the emergency stop is functional and will operate correctly in a real emergency situation. This practice is essential for maintaining safety standards and ensuring that all safety devices are in working order.

By routinely checking the emergency stop function, operators can identify any potential issues or malfunctions ahead of time, which can prevent accidents and injuries. It's important for operators to not only know where the emergency stop button is located but to also confirm that it effectively halts the operation of the stacker when engaged.

The other options touch on aspects of emergency stop usage but do not emphasize the critical need for regular testing, which is paramount for operational safety and compliance with safety protocols.