polyline p 4 0 0 10 0 0 10 0 10 8 0 10 8 0 4 6 0 4 6 0 6 4 0 6 4 0 0
mkplane f p
prism s1 f 0 5 0
polyline p 6 0 4 6 5 4 6 2.5 5 6 0 4
mkplane f p
prism s2 f 2 0 0
bfuse s s1 s2
explode s so; copy s_1 s
donly s

OFFSETSHAPE 2 {} $calcul $type

checkprops result -v 1116

checknbshapes result -shell 1
