Repair as a design detail
A visible joint can explain how an object might stay useful.
A joint tells a story about construction. A screw, a clip, or a glued seam can suggest how parts meet, but appearance does not guarantee easy repair. Access, replacement parts, and the order of assembly matter as much as the fastener you can see.
Start by looking at an object you already own, without taking it apart. Can you identify separate materials? Is a frequently worn part distinct from the main body? Is there a maker-provided repair guide? Those questions make a more grounded observation than assuming that any visible screw means the whole object is serviceable.
Keep electrical, pressurised, and safety-critical equipment closed unless you are qualified to work on it. The design observation is valuable on its own: understanding where wear is likely to happen helps explain why a small, replaceable part can matter to a much larger object.