Painted lines are the least ambiguous method for defining a precise boundary for a penalty area and while these will be put in for major competition, most golf courses don’t have the resources to maintain such course marking 365 days of the year.
Within their local rules they should describe how the edge of penalty area is defined. A physical characteristic can be used – most commonly “where the ground breaks down” (i.e. the change in slope at the edge of a ditch), or sometimes the stakes can be used to “define” the edge as well as “indicate” the status (i.e. red or yellow) of the penalty area.
The local rules on the scorecard at Brokenhurst Manor uses the following very common phrase:
Using stakes or physical characteristics both have pro’s and con’s. It is very difficult to mark a curvy penalty area with straight lines between stakes, but also the “break in slope” may not be sharp and so open to differences in interpretation.
This video is in response to a competitor, possibly used to a course where stakes DEFINE the penalty areas, who tried to claim that a large wooded area was all part of a penalty area. The summary is as ever – read the local rules before you play!
Golf Rules Guru 
Hi Stuart
I hope you are well? I notice the Local Rule doesn’t further advise that any unmarked penalty area is treated as a Red Penalty Area. As few golfers read the definitions might that not be a good addition?
Regards Fraz
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Yes – could well be. However we have made a pretty big effort to get at least 1 red post on every ditch. Preparing for the Brabazon qualifier this year we also found a (possibly our last) yellow post marking a ditch about 50 yards into the trees to the right of the 18th. Nobody knew the ditch was there (not even the greenkeepers) and surely nobody thought that crossing this ditch was part of the challenge of the hole to make it a non-lateral water hazard historically or yellow penalty area now?
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