At my airline, (a middle eastern major), our flight ops manual specifically provides instructions on, "Controlled rest on the Flight Deck". It specifically details planning, advice on what do for the pre-rest preparation, the rest period itself and the post rest period. We utilise it all the time as much of our flying is back of the clock with minimum rest periods between flights. In an ideal world we would actually have rosters that allowed fully rested crews to operate or augmentation for tiring flights on a much more frequent basis, but commercial necessity, it would appear, is king. At least we don't have to break the company's and regulator's rules to grab 40 winks and this, I believe, increases flight safety. Not perfect I know.
Night night,
HUB