The Back Lock is a progressive figure of 4 steps borrowed from Quickstep. It is very popular as the ending to a Progressive Chasse to Right.

As with most 4-step figures in Slow Waltz, the Forward Lock is counted "1, 2&3". It normally begins with man backing diagonal wall, with lady preparing to step outside partner. It can be repeated as desired (though the progression toward diagonal wall will tend to limit the repetition), and is followed by Closed or Open Impetus, Back Whisk, or Outside Spin, among others.

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