you know whats cool? i had those cranks too...they came stock on my bike when i bought it. and ya know what else? THEY HAVE A BOLT THAT THREADS INTO THE DRIVE SIDE ARM. thats how they work.

and the edge of the hole is that way from stress on the sprocket from you pedaling. there are signs of stress because its a peeeeeeeeeeeeeeeeice oooooooooooooooooooffffffffffffffffffffffffffffff shhhhhhhhhhhhhhhhhhhhhhiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiit