Identify a characteristic of column-and-knee milling machines.

Column-and-knee milling machines are recognized for their manual operation and the presence of adjustable worktables. This characteristic allows operators to easily move the workpiece and adjust its position relative to the cutting tool, providing flexibility and precision during the milling process. The knee of the machine can be raised or lowered to accommodate various workpiece heights, enhancing the machine's versatility for different sizes of materials.

While some milling machines can be automated, column-and-knee machines are traditionally designed for manual use, making this feature significant. A fixed spindle is associated with different types of milling machines and does not apply here. Additionally, column-and-knee milling machines do not utilize a circular saw for machining; instead, they use milling cutters that can produce a variety of shapes and surfaces in the workpiece.