An improved thru-wall structure useful for apparatus for processing photosensitive material for separating adjacent chambers filled with processing fluids. The wall structure having first and second wall portions and a pair of sidewall portions which define a passage opening. A pair of parallel contacting rollers are placed into the opening. The rollers have a compliant sublayer which elastically deforms in an radial direction and a outer layer made from a material having a low coefficient of friction to allow the rollers to be easily rotatably driven and providing a fluid seal between the rollers. The rollers are placed within the sidewalls by engaging the roller ends into an opening provided in each sidewall which is slightly smaller than the diameter of the combined rollers so as to provide a tight liquid seal at the roller end-sidewall interface.