How is a Lew attachment best described?

A Lew attachment is best described as a hinged locking device. This classification highlights its functionality in dental prosthetics, specifically in maintaining the stability and retention of overdentures or removable prosthetics. The hinged mechanism allows for some movement, accommodating the natural dynamics of the oral cavity while providing security for the prosthesis. This design is pivotal for effective oral function, as it permits slight adjustments without compromising the connection's strength and integrity.

In contrast, other options do not accurately represent the nature and function of a Lew attachment. A rigid connection implies no movement at all, which does not align with the design of this attachment. A screw-based system is more typically associated with elements that require precise torque and fixed positioning, which does not align with the operability of a hinged device. Lastly, describing it as a temporary anchorage does not fully encapsulate its primary purpose as a secure, stable connection designed for long-term use in restorative dentistry.