Sorry this took a minute to respond to, things have been nuts over here…

Okay! So, it’s actually a very simple design! The whole thing comes in two parts, like this:

On the left is the lock-shaped housing, on the right is the lockpick, which has all the numbers 1-20 arranged around the outer edge of the disc. The bottom of the lockpick disc comes to a point, like a spinning top, which is exactly what it is.

You thread the lock over the pick so the pick emerges from the keyhole in the lock, like this:

Now your lockpick die is all set. When it’s time to do a skill check, you hold the lock down with one hand for stability, and you twirl the lockpick with the other like a spinning top. After a moment, use your finger to nock the lockpick firmly down and reveal the result of your “roll”.

The window above the keyhole shows the number. In this case, I “rolled” an 18.

From behind, you can see the disc has teeth all around the edge, and there’s a point at the bottom of the lock that will catch between those teeth when you nock the pick to ensure it lands properly on one number instead of coming up between them.

And that’s how the lock-and-pick d20 works!