What's jock strap? Here's an extract from The catcher in the rye; He always brought out the old sadist in me. I was pretty sadistic with him quite often. Finally, I quit, though. I pulled the peak around to the back again, and relaxed. "Who belongsa this?" Ackley said. He was holding my roommate's knee supporter up to show me. That guy Ackley'd pick up anything. He'd even pick up your jock strap or something. I told him it was Stradlater's. So he chucked it on Stradlater's bed. He got it off Stradlater's chiffonier, so he chucked it on the bed.