Industry knowledge:
The screw head type is the first piece of information you’ll need to consider when figuring out what kind of screws you have or choosing the right kind of screws for your project.
You might choose a certain screw head type because of personal preference or for functional purposes. If you want a completely flush, flat appearance on the outside of the product you’re building, for example, then you’ll probably want to use a flat countersunk head. If you have a product with thick or strong outer walls, on the other hand, you’ll probably need a thicker screw head that rests on the outer surface of the product.