box b1 10 10 4
polyline p 0 0.5 4 0 2.5 4 10 9.5 4 10 7.5 4 0 0.5 4
mkplane f p
prism b2 f 0 0 4
bfuse s b1 b2
unifysamedom s s
donly s

OFFSETSHAPE 3 {} $calcul $type

checkprops result -v 3229.82

checknbshapes result -shell 1
