Stand up straight with a ladder laid out on the floor in front of you.
Stand to one side of the ladder.
Step sideways into the first square, then quickly bring your other foot to the same position.
Step your first leg out to the other side of the ladder, picking up your second foot from the square.
Repeat this movement in the other direction, stepping into the next square.
Do this exercise quickly, springing lightly off the balls of your feet.