Also unique to Tabula is the use of snapping to build dynamic relationships. For example, a point can be snapped to the midpoint of a segment and remain at the midpoint even as the segment is transformed. Teach the use of instruments like the compass, ruler, and protractor with working models. There are many tools built in to get you started--tools for midpoints, ellipses, perpendiculars, locus, and more. If the built in tools are not adequate custom tools can be made.