Calipers

They say in woodworking, "measure twice, cut once" to drive home the point of making sure your measurements are accurate before you start doing something permanent. One way to get accurate measurements is with a set of calipers. Calipers use a set of jaws as a start and end point to measure what's in between. Calipers are most often used in mechanical engineering, wood and metal working, science, medicine, hobbies and much more.