News outlets reserve the option to factcheck ads and will generally refuse to run an ad that is clearly false. This is apparently not the practice at the Washington Post (a.k.a "Fox on 15th Street).
The paper had a full page ad in the Sunday edition pushing the Keystone Pipeline. One of the claims in the add is that the unemployment rate among construction workers is 20 percent. If the Post had made the long trip over to the Bureau of Labor Statistics (BLS) website it would have discovered that the November employment report showed the unemployment rate among construction workers to be 13.1 percent. That is considerably higher than the national average of 8.6 percent, but still quite a bit short of 20 percent.
It is also worth noting some of the other misleading statements in the ad. It refers to 20,000 jobs that will be "directly" created by construction of the pipeline. Most of these jobs are not in the construction industry, but rather jobs along the supply line, for example in pipeline manufacturers or for truck drivers. While the economy can use these jobs as well, if we're looking at employing construction workers, the 20,000 figure is the wrong number. Direct employment in construction of the pipeline will be less than half of this number.
Finally, it is worth putting this figure in some context. BLS tells us that there were 1.1 million unemployed construction workers in November. If we assume (generously) that half of the 20,000 jobs mentioned in the ad are in construction, then the pipeline would reduce unemployment among construction workers by less than 1 percent. Note that this is 1 percent, not 1 percentage point. Assuming that the industry's numbers are accurate, construction of the pipeline would create enough jobs to reduce unemployment in the construction industry by approximately 0.1 percentage points.