Hi,
How hatched trapezoid MBCD ?

Best regards,

Fabrice

\starttext

\startMPcode
path p ;
p=unitsquare scaled 4cm ;
draw p ;
pair z ;
z=point 3.6 of p ;
draw z--urcorner p ;
label.llft(btex B etex,llcorner p) ;
label.lrt(btex C etex,lrcorner p) ;
label.ulft(btex A etex,ulcorner p) ;
label.urt(btex  D etex, urcorner p) ;
label.lft(btex M etex, z) ;
\stopMPcode

\stoptext