I have worked on Motorhomes with slide rooms since 1994. I worked on Newmar's since 1994. Newmar's with manual slide (props or lock arms) required them to be in place, until Newmar developed Electric lock arms. The reason was, the design of the Newmar slide room when retracted, the top was NOT sealed tight and the Lock arms pulled the top in that last inch to seal when retracted. Jayco's(towables and motorhomes) and National and early Monaco Class A's also used lock arms(props) to do the same thing and also to prevent excess movement when driving. I always told my customers when they asked your question---IF THE RV MAKER ENGINEERS AND BUILDS AND SUPPLIES LOCK ARMS THEN THEY ARE NEEDED. The rooms are not going to come out in transit. IF there is a malfunction the most a room will pooch out in transit is less than 6 inches. Usually less than 4 inches. I also have had customers come in and complain about excess slide noise/squeaks/rattles. I ask them if they are using the supplied lock arms/props. NO, they stated "experts" on line and campgrounds stated they were not needed.:B I install the lock props/arms and we test drive. Customer realizes that they WERE needed. Of course it cost the customer $100 for me to explain and show and test drive. Doug
