I'm here to explain the much needed VPL tag; otherwise known as Visible Penis Line. It describes for when in a picture a visible line can be shown in a Bulge of either underwear, pants, shirts, anything that can form an outline that forms an outline around the penis and hence causes a Visible Penis Line; VPL. An implication with the Bulge tag since you can't have VPL without a little Bulge.
It's important to have this own tag since Bulge is just any generic bulge between a guy's legs; even the bulge of muscle in some cases. But VPL would be tagged in images where you can make out exactly where the penis is instead of solely a generic area. It'd also work for outlines of sheaths and balls since some artists draw the underwear a bit too tight.
Updated by Clawstripe