Using the Deltana 4 - inch flush bolt is easy. First, measure and mark the correct position on your double doors. Then, install the bolt with the provided screws. Make sure one door stays inactive by engaging the bolt properly. When using, gently push the door to engage or disengage the bolt. As for maintenance, wipe it regularly with a soft, dry cloth to keep its finish looking good. Avoid using harsh chemicals or abrasive materials as they can damage the brass. If you notice any looseness, check and tighten the screws. Also, keep the moving parts lubricated with a light oil to ensure smooth operation.