This chapter considers some rather special joints and connections used primarily for affixing membranes, diaphragms, and barriers to their supports. It describes an experiment for measuring diaphragm displacements. The relevant barriers acting as mechanical joints can involve bolted, welded, or adhesive elements designed to resist complex stress interactions often caused by large deformations and membrane-type forces in barrier walls. The choice of membrane materials includes a wide range of properties with polymers (plastics) supplementing those requirements where a viscoelastic behavior may be of special importance. Diaphragm, however, usually implies a thin membrane in tension acting across a given pressure drop. Thin circular membrane under pressure develops an approximate spherical curvature and the middle surface undergoes a significant straining. Large deflection theory of plates can be used to predict the membrane stresses and maximum deflections. Larger diaphragms are likely to fail by pull-out at the support prior to reaching the maximum membrane at the center.