\makeatletter \def\TopRule{\noalign{\ifnum0=`}\fi \@aboverulesep=\abovetopsep \global\@belowrulesep=\z@ \global\@thisruleclass=\@ne \@ifnextchar[{\@BTrule}{\@BTrule[\heavyrulewidth]}} \def\MidRule{\noalign{\ifnum0=`}\fi \@aboverulesep=\z@ \global\@belowrulesep=\z@ \global\@thisruleclass=\@ne \@ifnextchar[{\@BTrule}{\@BTrule[\lightrulewidth]}} \def\BottomRule{\noalign{\ifnum0=`}\fi \@aboverulesep=\z@ \global\@belowrulesep=\belowbottomsep \global\@thisruleclass=\@ne \@ifnextchar[{\@BTrule}{\@BTrule[\heavyrulewidth]}} \makeatother