Self-opening and closing three-folding umbrellas are designed with several key points in mind to ensure their functionality and convenience. Some important design points are:

1. Compact size: Three-folding umbrellas are designed to be compact and easy to carry. They are often small enough to fit into a purse, backpack, or briefcase, making them a convenient option for on-the-go use.

2. Automatic open and close mechanism: Three-folding umbrellas feature an automatic open and close mechanism, which allows for quick and easy deployment and retraction. This mechanism often operates with a simple button press.
   

3. Sturdy frame: The frame of the umbrella is designed to be sturdy and durable, with the ability to withstand strong winds and other adverse weather conditions. The frame is typically made from materials such as fiberglass, aluminum, or steel.

4. Comfortable handle: The handle of the umbrella is designed to be comfortable to hold, with a non-slip grip that provides a secure hold, even in wet conditions. Some handles may also feature ergonomic designs for added comfort.

5. Waterproof canopy: The canopy of the umbrella is designed to be waterproof and wind-resistant, with the ability to repel rain and other types of precipitation. The canopy is typically made from materials such as nylon or polyester.

6. Stylish design: Three-folding umbrellas often feature stylish and eye-catching designs, with a range of colors and patterns to choose from. This makes them a fashionable accessory that can complement any outfit.

Overall, self-opening and closing three-folding umbrellas are designed with a focus on convenience, durability, and style. They are a popular choice for individuals who need an umbrella that is easy to carry, quick to deploy, and able to withstand adverse weather conditions.