What should I do if the screw cap has no edges?

What should I do if the screw cap has no edges? This is a problem that many people often encounter when using a wrench to remove screws. In daily life, screw caps often become rusty due to long-term use or being soaked by rain, causing their edges and corners to be smoothed and difficult to disassemble. So how to solve this problem?
First, we can choose to use a professional screw extractor. This tool usually contains a specially designed screw bit that squeezes the screw cap, causing it to bend and slowly loosen, allowing you to easily remove it. The trick to using this tool is to first drill a hole in the screw cap, then attach the screw extractor to the electric drill, insert it into the hole, and rotate it at a slow speed until the screw cap gradually loosens.
But don't worry if you don't have the right tools available. We can also try the following tips:
First, you can try spraying some lubricating oil. Using lubricant can help you reduce friction, making it easier for the screw cap to loosen. According to the instructions, spray the lubricating oil around the screw cap and let it fully penetrate, and then use a wrench or other tool to try to loosen the screw cap.
Second, if the screw cap is very tight, you can use a rubber band. Wrap the rubber band around the screw cap and tighten with a wrench. This allows you to loosen the screw cap more easily due to the greater friction of the rubber band.
Third, you can use a metal hammer to tap the screw cap. Before use, please soak it slightly in warm water, this can make it expand more easily, making it easier to loosen. Then, use a metal hammer to gently tap the screw cap. Please pay attention every time you hit to prevent greater damage.
Fourth, if all the above methods fail, you can try carving a cross shape. Using a knife or other tool to carve a cross shape on the screw cap will help you loosen the screw cap more easily. Just use it carefully so as not to weaken the screw's strength.