A trailer flange is used to transfer a 35mm trailer from a non-standard core to a projection reel. It is functionally similar to a split reel, but can only be used in conjunction with a 1" trailer core.
Trailer cores cannot be placed directly on a standard Kelmar spindle for the purpose of film inspection. Trailer cores also do not fit on a standard split reel; they can only be used in conjunction with a trailer flange. Once the trailer core is seated on the trailer flange, the film can be wound onto a standard reel.