  We propose a new kind of seismic diagram, based on the determination of the
locations of sharp acoustic features inside a star. We show that by combining
the information about the position of the base of the convective envelope or
the second helium ionisation zone with a measure of the average large
separation, it is possible to constrain the unknown parameters characterising
the physical processes in the stellar interior. We demonstrate the application
of this technique to the analysis of mock data for a CoRoT target star.
