In a module unit in a housing, the module unit is designed to easily slide into and out of the housing. The housing has one or more plenums through which convective air circulates around and through the module unit. A sealing mechanism seals openings that connect the module unit and one or more of the plenums. When the module unit is removed from the housing, a lift mechanism removes the sealing mechanism from the openings, and allows the module unit to be easily removed from the housing. After reinsertion of the module unit, the lift mechanism reinserts the sealing mechanism into the openings.