The definition "Plankedør sammenholdt af to tværgående og en skrå revle"
is precisely the phrase used in Hovmand & Andersen's Illustrated Building Dictionary.

Ledge: one of the two or three horizontal timbers on the back of a matchboarded door

revle (skråbånd): brace

The drawings make it quite clear - and I can warmly recommend the dictionary. It is not expensive in Denmark, though it might not be so easy to get hold of 'down under'
ISBN 13: 9788 7987 03426
ISBN 10: 87-9870 34 2 0


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Note added at 2 hrs (2009-05-08 12:14:38 GMT)
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It seems to be a
Z-braced battened door

There is a battened door here:
http://www.answers.com/topic/battened-door-1

It mentions the diagonal brace, (revle) but the drawing does not show it.