The retractable shower door you ordered was correctly sized at 35.5" in height, but the top and bottom rails were mistakenly manufactured at 37.5" width. Since your order was placed for 35.5", you have two options to resolve the issue. First, you can use a metal saw to trim the rails down to the correct 35.5" width yourself, which is the method the manufacturer would use if the parts were returned. Alternatively, you can send the rails back to have the manufacturer resize them precisely to your custom measurements, though this option will require additional time. Either choice will ensure your shower door fits your RV frame as intended. Contact Elkhart RV Parts to arrange a return or get further assistance.