Pan head machine screws have slightly rounded heads with short vertical sides. They are typically used with nuts or drilled and tapped (threaded) holes. You could see them around because they are widely used in a variety of industries such as construction, manufacturing, engineering, assembling and so on. The Phillips drive has an x-shaped slot that accepts a Phillips driver and is designed to allow the driver to slip out of the head to help prevent over-tightening and damage to the thread or fastener. The high quality 304 (18-15) stainless steel provide perfect strength and good corrosion resistance in bad environments like high temperature, cold weather and high humidity areas without the need for time consuming and costly maintenance.