Place a bench vertically on the floor. You stand at the short end, facing the bench. Take one dumbbell, any weight you choose, and place it between your feet. Make sure that the weight is secure.
Without losing the weight between your feet, walk your hands up the bench so that you end up in a prone (facedown) position.
Now all you have to do is squeeze those inner thighs together to keep the weight in place. At the same time, tighten up your abs to support the lower back. Finally, do some hamstring curls. Vary your counts! For example: