A module is retained in a slot of an electronics chassis. A clearance space is provided for receiving the module in a slot of the electronics chassis by controlling an internal pressure of a bellows. The bellows forms a part of a retainer that is disposed on an elongated rail extending along a length of the slot. The bellows defines an internal bellows capsule which contains a fluid. Once the module has been inserted in the slot, the module is secured with the retainer by further controlling the internal pressure of the bellows to exert a force on the module.