What does an upside-down U weld symbol indicate?

The upside-down U weld symbol is indicative of a convex weld. This symbol is used in welding blueprints to specify that the weld bead should have a rounded profile, bulging outward from the base material. A convex weld profile can be advantageous in various applications, as it helps with the flow of liquids over the surface and can be more aesthetically pleasing.

In this context, understanding the difference between the profiles is crucial. A concave weld, for instance, has a recessed shape that curves inward, which is not represented by the upside-down U symbol. Similarly, bevel and square weld symbols convey different concepts related to joint preparation and angle rather than the profile of the weld itself. Thus, recognizing the characteristics associated with this particular symbol reinforces the importance of precise nomenclature in welding and fabrication.