11.1 Centerline, Leftline, Rightline

<..latex ltboxes..>+
 \NewConfigure{centerline}[2]{\c:def\cnt:a{#1}\c:def\cnt:b{#2}}
 \NewConfigure{leftline}[2]{\c:def\lft:a{#1}\c:def\lft:b{#2}}
 \NewConfigure{rightline}[2]{\c:def\a:rightline{#1}\c:def\b:rightline{#2}}
 -_-_-