The author uses geometrically definable shapes for mobile members in such a way that equations can be written for moment balance to yield analytical solutions for determining the suspension points of the members. This avoids the need for trial-and-error construction. Geometrically definable shapes also make it possible to use jigsaw layout of mobile members to minimize waste of materials. The author finds that these two “constraints” add an intellectual dimension to mobile-making. To facilitate the realization of a mobile maker's conceptualization of shape and motion in space, the author recommends small indoor mobiles, which can be made to respond to weak air currents such as those produced by body movement and human breath.