The present invention provides switchable adhesives comprising a mixture, in proportions by weight, of 20% to 98% of an adhesive, 2% to 80% of curable molecules and 0. The engagement member moves within the lock body to engage the threaded member in at least two different positions. By employing operative units which can be internally varied to provide different thermal capacities within form factor constraints, the system enables concurrent temperature control needs of a number of different units to be met with an energy efficient, low footprint, highly adaptable system. In a preferred embodiment, the non-refractive region forms a vertical column on one end of the lens sheet and the refractive region forms a vertical column on the other end of the lens sheet. The threshold may be a multiple of a maximum phase-to-phase current. Other apparatuses for opening and closing a barrier are also described.