We often use the word flange to describe something associated with an RV part. However, it’s not an easy concept to describe and is not as common a word as to when it was used most often (in around 1910.)
The dictionary definition of the word flange (plural flanges) is “a projecting flat rim, collar, or rib on an object, serving to strengthen or attach or (on a wheel) to maintain position on a rail.
An example use of flange in a phrase would be "the flanges that held the tailpipe to the aircraft". Here are some images of basic flanges:
In the RV world, the most common use of the word flange has to do with RV slideout rooms. This is the flat “frame” surrounding the outer face of the slideout room. This flange is the part that sits up against the side of the RV when the slideout room is in (but doesn’t go inside the RV body.
We need the measurement of the flange to fit tip-out rooms for slide-out awnings. We use the width including the flange in conjunction with the width of the actual room itself to determine the best width of the Slidetopper awning. We also need the height of the top flange to determine whether the installation requires a tall or short Slide Topper mounting bracket kit.
Lots of other RV parts and accessories have flanges too, like:
RV Fresh Water tank Draincocks
Flush mounted RV LP Gas detectors
RV Faucet Flanges
Trailer Axle Hub Flanges
RV Toilet Flanges
RV Waste Holding Tanks
RV Fresh Water Tank Inlets