What does a universal cylinder refer to?

A universal cylinder refers to a cylinder that has been specifically designed to be connected for service in either vertical or horizontal positions. This versatility is important for various applications, as it allows users to utilize the cylinder based on the spatial constraints and requirements of their setups. The ability to function effectively in both orientations enhances convenience and adaptability, making it suitable for a wider range of uses compared to cylinders limited to one orientation.

In contrast, the other options describe more restrictive functions or characteristics. A cylinder only usable in vertical positions is limited in its application and versatility. A cylinder designed only for specific applications does not offer the broad usability associated with a universal design. Lastly, a cylinder that cannot be transported would not align with the concept of a universal cylinder, as the ability to transport and connect the cylinder in multiple positions is a key defining feature.