A Saturday night ride is usually accomplished in these steps:
1) The wrestler takes his opponent to his back, wraps both legs around his opponent's legs, and spreads them out wide.
2) The wrestler on top arches his back and presses his chest and hips down into his opponent in order to hold him down on the mat.
3) The wrestler on top wraps both of his arms around his opponent's arms, or grabs one of his oppponent's arms and wraps his other arm around his opponent's head and pulls it up.
4) With both legs trapped and with his whole body held down, the wrestler on bottom can't do anything to escape. When the wrestler on top holds both his shoulders or shoulder blades down on the mat long enough, the wrestler on bottom is pinned and the other dude wins.
5) If a wrestler does this move well enough, it's not only a guaranteed pin, but also a good way to own and embarrass the other dude, if you want to do that.
Since the Saturday night ride has both wrestlers flat on the mat with their legs and arms wrapped around each other, it often looks like a sexual position, hence the name.
The move is also known as the "Saturday night," the "double grapes," the "angel," or the "honeymooner."