In message , Clive Coleman
writes

We were taught to use a square with a clip to attach it to the coupler
called a presspahn (If I recall correctly) which covers the "Dutch
oven" to allow a mechanical couple without an electrical couple. One on
each side of the coupler.

Oh yes we have those for when we want to mechanically couple only in
emergencies (double ended units as single enders only have mechanical
couplings anyway).

The OP was talking about being able to couple A-A or D-D and the Dutch
ovens wouldn't match up anyway.
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