polyline p 0 0 0 4 0 0 4 0 1 2 0 1 1 0 3 1 0 4 0 0 4 0 0 0
mkplane f p
prism s f 0 5 0
explode s f
donly s
offsetparameter 1e-7 c i 
offsetload s 1
offsetonface s_4 3
offsetperform result

checkprops result -v 233.186

checknbshapes result -shell 1
