Which tool does not belong to the group of measurement instruments?

The correct answer identifies a tool that is not primarily used for measurement. A double VEE block is a fixture used primarily for holding or locating workpieces in machining processes, especially in setups for welding, grinding, or other manufacturing operations. Its design allows for the stable and accurate positioning of components, facilitating processes rather than measuring dimensions.

On the other hand, tools such as hermaphrodite calipers, dividers, and trammels are specifically designed for measurement tasks. Hermaphrodite calipers are used to transfer measurements and establish distances, dividers are employed for marking equal distances on materials, and trammels assist in drawing arcs and circles to specified dimensions. Each of these instruments is critical in measuring dimensions or ensuring precision in layout work, which distinguishes them from the double VEE block, whose primary purpose is not measurement but rather positioning.