What is the purpose of a universal socket?

A universal socket is specifically designed to accommodate various sizes and shapes of fasteners, allowing for versatility in different applications. The primary purpose is to turn multiple types of fasteners, including nuts and bolts, regardless of their specific shape or size. This characteristic makes it particularly useful in situations where space is limited or where a user needs to work with various fastener types without needing to switch tools constantly.

In contrast, the other options describe functions that do not align with the core capability of a universal socket. Holding screws pertains to devices like screwdrivers or screwdrivers with specific heads designed for that purpose. The use on flat surfaces is more aligned with tools that provide stability for cutting or smoothing, such as a level or square. Measuring torque is a function associated with torque wrenches, designed specifically to apply a precise amount of force to fasteners. Thus, the correct answer highlights the multifunctional aspect of a universal socket in handling multiple fastener types, emphasizing its practicality for users who frequently encounter diverse work scenarios.