Screws are used to hold materials together and if they’re not the right kind for a specific job they can bend, break or work themselves loose. This can cause serious damage to your project, so it’s important to use the right screws for each material you need to screw into. There are 13 different types of screw available for many different projects and materials including wood, drywall, concrete and machinery. Each type has a different purpose and is used in varying thicknesses of materials. They also come in a wide variety of head types, drive types and lengths.

Screw sizes are based on the diameter of the screw thread and the number of threads per inch, as well as the length. Screws are often labelled with their gauge size, thread count and length on the packaging in imperial and metric systems. For example, 3/8”-16 is a machine screw with a major diameter of 3/8″ and a thread count of 16 threads per inch.

If you’re using a screw that has a flat head, you can measure the diameter by holding a stick or straw against it. You can then look at a screw gauge chart to find the decimal equivalent. Screws with a smaller major diameter are usually labeled in inches (#0 up to #14), while larger ones are numbered in fractions of an inch.

For metric system measurements, the screw will normally be listed with its gauge first and its length second. For example, a package of screws that say “10 x 2″ means the screw has a 10 gauge with a length of 2 inches. 1/4 lag screw pilot hole