In this paper we use geometric tools to establish controllability properties of driftless systems which have less control inputs than states, but whose input vector fields span a non-involutive distribution. Our prototypical class of systems is conformed by kinematic models of non-holonomic systems such as the unicycle or a car with N trailers. We restrict our class of inputs to those which are piecewise constant. The restriction gives way to an easy implementation in discrete time and allows to formulate control problems as systems of polynomial equations. The control problems can then be addressed using geometric-algebraic tools and can be solved explicitly using symbolic computational software if their size is reasonable.