Technology is a good thing, but sometimes it can be confusing. Such is the case with all the fasteners available today. A brief walk through the hardware store will reveal bin after bin of dozens of different types of fasteners. Here is a brief primer on fasteners to help you understand when you need a screw versus a bolt versus a nail.
Simple nails have been used for thousands of years. In fact, bronze nails have been found in ancient Egypt. Nails were originally hand forged, which gave them a square shape, but they have been mass-produced for about the last 200 years, giving them the typical round shape known today.
A nail is best used for construction projects that don't require a lot of strength. Most nails are made of steel, and they are typically used on wood or other lightweight materials. Box nails and common nails are two typical nail types used in light construction jobs, such as nailing down shingles or siding. Finishing nails have a very small head. This allows them to be used in things like baseboards or other trim work as they are easy to hide and won't take away from the overall aesthetic.
Other nails, such as roofing nails, are made with steel that has been galvanized to prevent rusting. Nails are occasionally used in masonry projects where strength isn't required. Masonry nails are made from hardened zinc, so they have the ability to stand up to masonry materials.
A bolt is used anytime significant strength is required. Whenever a construction project can be considered heavy-duty, bolts, and their partner, nuts, are used. Homes and other buildings are built with nuts and bolts. Nails and screws simply can't support the massive weight put on joints by people, furniture, and the building materials themselves.
Bolts are typically made in one of three metals. Stainless steel bolts don't need any protective coatings as they are naturally resistant to corrosion. Carbon steel bolts are plated in zinc to provide extra resistance. Bolts that are made from a steel alloy are coated with cadmium and are extremely strong. These are used in heavy construction, such as multi-story buildings. Bolts can also be used with metal and mechanical parts. Because there are so many bolt and nut combinations to choose from, an expert opinion should be sought for each project to ensure you choose the right combination. For example, if one's project requires a moving part, you may need shoulder bolts to accommodate the rotation.
A screw is like a miniature bolt. It is a better choice than a nail when you are doing things like building kitchen cabinetry or furniture. They are screwed or drilled into a material rather than pounded with a hammer as nails are. In addition to screws suited for wood, there are other types, such as those for drywall or plastic.