When I teach people how to do visual examinations as part of the original stage of a failure investigation, I remind them of a very basic group of things that are truly facts.
A screwdriver might be described as a long, skinny cylinder with a larger-diameter cylinder at one end. We’ll often find that the large-diameter end is rounded, while the tip of the skinny end is flattened. We will often find that the large-diameter end is made of a lighter (less dense) material than the skinny end. The long, skinny end might be silvery in color, while the larger end might be any of a number of colors.
While we are doing this learning exercise in a live class, the students are not allowed to say, “This is a screwdriver.” Even more important would be not being allowed to say that when viewing only a photo. A photo of a screwdriver does not permit driving a screw. Even something that looks like a screwdriver and feels like a screwdriver could be a fake. A screwdriver implies a certain functionality. We can think it looks like a screwdriver, but that’s an opinion. But the fact that the skinny end feels cool after a short time of handling, while the thicker end is warm are facts. The apparent colors are facts, although they could change if the light changes, and individuals see colors differently. Smooth and rough surface finishes, uniformly colored or blotchy are facts that can be stated and then, given the same physical objects or data sets, others can rapidly confirm the accuracy or not, simply based on sensory information.
Test your skills with the image above. Pick one of the screwdrivers shown and describe it using only features that you can see or could see or feel if you had it in your hand. That would include shapes, colors, textures, temperature, weight. What details can you see here that were not mentioned in the text article? Tapers or flared features on the large-diameter end? Circumferential grooves at the end of the large-diameter portion where it meets the small diameter? What about that apparently square section on the largest screwdriver? Do all of these tools have flattened, skinny end tips?
Read your description to a friend or spouse and see if they can figure out that it’s a screwdriver. Try with some other simple object. No material identifications. Just sensory impressions.