  In our previous paper, we presented the combinatorial theory for minimal
isostatic pinned frameworks - Assur graphs - which arise in the analysis of
mechanical linkages. In this paper we further explore the geometric properties
of Assur graphs, with a focus on singular realizations which have static
self-stresses. We provide a new geometric characterization of Assur graphs,
based on special singular realizations. These singular positions are then
related to dead-end positions in which an associated mechanism with an inserted
driver will stop or jam.
