Just before the bad guys break into the house, Kevin puts tar on the basement steps. Once Marv makes it to the steps he tries to walk on them. First his shoes get stuck and then his socks and he ends up trying to walk up the stairs in bare feet, meanwhile getting his bare feet covered in tar. Anyway, he steps on a nail and falls. If his shoes and socks got stuck to the tar, why don't his feet get stuck to anything when he walks?