Tight white briefs that are comfortable and hold your balls and penis into a fixed position so that they don't sag.
I was changing in the locker room when the cool kids came over and pantzed me (no one usually saw because I covered it with my shirt) showing my tighty whiteys. They took me and gave me a HUGE wedgie which gave me a boner. They then pushed through the lockerroom doors and the hot girls saw my TWs. I was SO embarressed.