Grab Zack's hands and hold them behind his back

"Come on dude," Alex snickered, "don't be shy!"

Alex grabbed Zack's hands and wretched them free from his soccer shirt. The fabric bounced back into shape, showing off Zack's bulge in the tight pouch of his jockstrap. Holding both of Zack's hands behind the embarrassed jock's back, Alex began pushing Zack twords the laughing crowd.