The Forward Lock is a progressive figure of 4 steps borrowed from Quickstep, and in reality seldom-used in Waltz. It's cousin, the Back Lock, is far more popular.

As with most 4-step figures in Slow Waltz, the Forward Lock is counted "1, 2&3". It normally begins with man facing diagonal wall, preparing to step outside partner following a Chasse from PP, Outside Change, Weave or Closed Telemark, and can be repeated as desired (though the progression toward diagonal wall will tend to limit the repetition). It should ultimately be followed by 1-3 Natural Turn (or any figure that begins as such) with the first step taken outside partner.

The man takes two steps forward, first with the right foot in CBMP, outside partner, then with the left foot diagonally forward. He then crosses, or "locks" his right foot behind his left, and then steps once again diagonally forward on the left to end in the same position he began. The lady's part is the natural opposite. Note that her left foot is crossed in front of, not behind the right foot on the third step.