Ever been outted by your cock? Gotten an obvious erection in front of a guy who didn't know you were attracted to men?
Sort of. Not by my erection*, but by my soft bulge. At a training function we had to put on harnesses similar to climbing ones that, ahem, emphasized whatever one had going on with their crotch, and it made my bulge look really obvious. I had a female co-worker ask what was going on, and she meant my crotch. I told her 'nothing' and to stop looking at my crotch.
*= as for erections, if I feel one coming on I just pop into a bathroom and put it in my underwear elastic