For most of the video slot machines, this means that after an initial spin of the reels, the player is allowed to lock selected reels in place and spin again, holding reels with valuable symbols in hopes of matching them up with winning symbols on the second spin. The compact with North Carolina requires games to have an element of skill. Thanks everyone! From Wikipedia: Since the tribe's compact with North Carolina restricts the types of gaming permitted, most of the games offered have significant differences with those found in other casinos.
