The sthanak is the plain hall used by the Sthanakvasi Jains, and it is best defined by an absence: there is no image in it.
Worship without an image
The Sthanakvasi are the Svetambara reform tradition that rejects image worship, holding that the veneration of consecrated images has no warrant in the earliest teaching, and their place of assembly reflects the conviction directly. The sthanak is a simple hall for prayer, recitation, meditation and the hearing of ascetics, containing no shrine and no image to be bathed or adorned, so that devotion is directed to the qualities of the liberated soul rather than to a represented form. The austerity of the building is the doctrine made architecture.
A reform within a reform
The tradition arose from a series of aniconic reform movements within Svetambara Jainism from the fifteenth century onward, of which the Sthanakvasi and the later Terapanthi are the principal survivors, set against the image-worshipping Murtipujaka majority whose temple is the derasar. The Sthanakvasi are also marked by the mouth-cloth, the muhapatti, worn permanently by their ascetics, a further sign of a tradition that has pressed the Jain principles of non-violence and non-attachment toward their strictest expression. The sthanak thus stands within Jainism as the deliberate counterpart to the ornate temple, worship stripped of the image the reformers judged a later accretion.