Hello everyone. Im Adam...and now that intro's are over, serious stuff(as if sitting on my ass all day programming games noone will ever see is serious anyways)

I am programming a 2d side-scrolling platformer. I have a functioning gravity routine, sort-of, which brings me to my problem. I have it checking the bottom left portion of the sprite for detection, but I need it to use the whole bottom of the sprite. I have tried a few things, but to no prevail. Any ideas, or some sample code?