Without addressing the fallacy of 'height means greater jumping ability,' the reality is that a majority of rebounds are garnered beneath the height of the rim, rather than above the rim. Because of this fact, height, to a certain extent, becomes a non-factor. The great rebounder recognizes that space is best created by widening his base, i.e., assuming a strong, poised, athletic crouch and using his posterior and hips to move his opponent farther away from the path of a rebound. A higher jump, and/or a height advantage, is negated by distance. This is what it means to "block out."
Get lower and wider than your opponent. Use this position of strength to clear out space. Stay wide, and forget about whether you're tall, or not. Width equals space equals rebounds equals success.