Intirtool’s patent on pliers for punching and connecting overlapping sheets of metal is not invalid for failing to comply with written description requirement because a claim’s preamble should only be read as limiting when it recites additionally structure or steps underscored as important by the specification. Also, because the Federal Circuit does not read the preamble as a limitation, there cannot be inequitable conduct because there is neither materiality nor falsity. Finally, Intirtool is not barred by latches because the latches clock cannot start until a pantentee has constructive or actual knowledge of an act of infringement that gives rise to a legal claim.