# Finding Edges with the Caliper Tool

The Shape Finding tools find edge points of a shape by repeatedly calling the Caliper tool. An important part of using the Shape Finding tools is selecting the right number of calipers. Calipers should be chosen so that the shape edge you wish to find is the only edge inside the caliper. If the caliper input region contains multiple edges, you should ensure the caliper is configured to find the desired edge first.

You must provide the Caliper tool run-time parameters each shape finding tool uses. For example, you would run the Caliper tool in single-edge mode to find the image on the left, while the image on the right has two edges and requires that you either run the Caliper tool in edge-pair mode, or that you specify the polarity of the expected edge explicitly.