Jenny calipers are different from other calipers as they are not used primarily for measuring. Instead, they are a useful tool for layout work such as marking a line a set distance from the edge of a part.

They are similar to compasses but have the advantage of a locating lug that allows the user to securely position the tool on one side of the workpiece.

The user can also be more confident of the accuracy of their scribed lines or centre marks.

This feature makes it easier to carry out layout tasks. The user can also be more confident of the accuracy of their scribed lines or centre marks.