Was feeling OK until I read this at alwaystestclean.com:

"Between 5 minutes and 10 minutes any faint line on the test region (T) could indicate that the drug in the sample could be near the cut-off level for the urine drug test. However, any line in the test area (T), no matter how faint, might be interpreted as a potentially positive test."
I went to check out that site and apparently it is down. But regardless, the info is incorrect. On any assay, a line in both the "C" window and the "T" window (regardless of intensity) is a negative.

To conclude that a faint line is indicative to being near the cutoff would be sheer speculation, since assays lack the ability to yield a quantitative analysis (unlike the GC/MS test).

And wrongly so as well. Even synthetic urines, which contain no drug metabolites at all, can produce a faint line on an assay.