About the Constraint Command Contact constraint can be created between either two elements. These constraints are in priority: Concentricity Coincidence Tangency Use the context menu if you want to create other types of constraints.
Constraint Types According to the elements you select, a single type of constraint is proposed to define the contact. A point and a line: Coincidence Two circles: Concentricity Two lines: Coincidence Two points: Coincidence A line and a circle: Tangency A point and any other element: Coincidence Two curves (except circles and/or ellipses) : Tangency Two curves and/or ellipses: Concentricity