There were never any male contestants on the show. Producers were afraid of how a man might react in a worst case scenario, so they decided to use women only as contestants.
To ensure no contestant found out what she won before it's time, there were never any cue cards. During commercial breaks, the contestant was secluded offstage while Geoff Edwards did a rehearsal of the sketch (if any - -the $25,000 box had no sketch).
Emile Autuori, the "bonded security agent" seen at the start and end of every episode, had been a security guard assigned to the ABC studio parking lot when Geoff Edwards asked him if he wanted to appear on the show. To hide the $25,000 grand prize check, he drew a number at random (with a member of the network's standards and practices department observing), and curtains were drawn around the set while he put the check in that box. The only person he told was director John Dorsey, so that Dorsey could be ready to brief Edwards in case a contestant picked the $25,000.