I've got some lake sandals (a shimano footbed) and I've got my cleats and pedals and I'm ready to go! Except for one thing. There is some sort of cover (i.e. square piece of rubber) that seems to cover upwhere the cleats would screw in. How do I get it out?? I've tried to pry it up with a knife but I didn't want to try too hard for fear that I'm doing it wrong. I know this is a simple thing but I'm a total dork, apparently. Thanks!