The design of a 3-pole Swiss plug insert is based on several key points. Here are some of the design points of a typical 3-pole Swiss plug insert:

1. Electrical safety: The plug insert is designed to meet strict electrical safety standards. The design must ensure that the electrical contacts are properly insulated and that the plug insert can handle the voltage and current requirements of the connected device.

2. Compact size: The plug insert must be compact in size to ensure that it can be easily plugged into electrical outlets in a variety of locations. The design must also ensure that the plug insert does not block adjacent outlets when plugged in.
   

3. Robustness: The plug insert must be designed to be robust and durable to withstand frequent use and transportation. The design should include features such as strain relief to prevent damage to the electrical cord and solid construction to prevent damage from impacts.

4. Ease of use: The design must be easy to use, allowing users to easily insert and remove the plug from an electrical outlet. The design should also ensure that the plug insert can be easily identified and distinguished from other types of plugs.

5. Compliance with standards: The plug insert must comply with relevant standards and regulations, including the International Electrotechnical Commission (IEC) standards and Swiss standards. This ensures that the plug insert is safe and reliable for use in Switzerland and other countries that use the same plug and socket system.

Overall, the design of a 3-pole Swiss plug insert is focused on ensuring electrical safety, compact size, robustness, ease of use, and compliance with relevant standards and regulations.